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What does ImportError mean in Python?
Question: I try to import a module:
import cv
And I get the following error message:
ImportError: DLL load failed: The specified module could not be found.
But if I try to import a library that definitely does not exist, for example:
import blabla
I get:
ImportError: No module named blabla
So, I conclude the the `cv` library is not totally hidden. Python is able to
see something. Does anybody know what Python is able to see and what is
missing?
**ADDED**
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
**ADDED 2**
In the directory that contains the `cv` library there is sub-directory
(`C:\OpenCV2.2\bin`) with many `*.dll` files. So, I tried:
import sys
sys.path.append("C:\OpenCV2.2\bin")
and I still get the "dll load failed". Is there a way to find out which
exactly "dll" file is missing. I mean, Python tries to find a specific dll
file (let say cv.dll) and cannot find it?
Answer: In this particular case, "DLL load failed" is caused by using Python 2.6 with
OpenCV 2.2. You should use Python 2.7, because cv.pyd is linked with
python27.dll.
|
Python hashlib.md5 and ejabberd
Question: I am using a python script as an external auth option in ejabberd 2.1.6.
I wanted to start encrypting the clear text passwords that come across in the
auth verification, so that they are not being stored in plain text in the
backend database. When I add the following code to my python script and
restart ejabberd, it hangs:
import hashlib
clear = "barfoo"
salt = "foobar"
hash = hashlib.md5( salt + clear ).hexdigest()
Does hashlib require specific priviledges to run?
When I run it as a normal user (ejabberd) it works without issue. When the
python script is run within the external auth of ejabberd it hangs.
I've attempted to have it write out the 'hash' to a file and it never gets
there ... if i run it as the 'ejabberd' user, it writes out to file fine.
I've tried to find information about restrictions for using this library on
ubuntu without any success. Any ideas?
-sd
** 22.02.2011: Here is the full script adapted from <https://git.process-
one.net/ejabberd/mainline/blobs/raw/2.1.x/doc/dev.html#htoc8> :
#!/usr/bin/python
import sys
from struct import *
import hashlib
def from_ejabberd():
input_length = sys.stdin.read(2)
(size,) = unpack('>h', input_length)
return sys.stdin.read(size).split(':')
def to_ejabberd(bool):
answer = 0
if bool:
answer = 1
token = pack('>hh', 2, answer)
sys.stdout.write(token)
sys.stdout.flush()
def auth(username, server, password):
clear = "barfoo"
salt = "foobar"
hash = hashlib.md5( salt + clear ).hexdigest()
if (password == hash): return True
else: return False
def isuser(username, server):
return True
def setpass(username, server, password):
return True
while True:
data = from_ejabberd()
success = False
if data[0] == "auth":
success = auth(data[1], data[2], data[3])
elif data[0] == "isuser":
success = isuser(data[1], data[2])
elif data[0] == "setpass":
success = setpass(data[1], data[2], data[3])
to_ejabberd(success)
Answer: I looked into the hashlib
[source](http://svn.python.org/view/python/trunk/Modules/_hashopenssl.c?view=markup)
and while it does not seem to require too much, it does import .so files as
modules and one of them hits openssl. It all looks pretty safe but if ejabberd
tries to fence itself against calls to 3rd party code (or if you have SELinux
or something else to that effect running), stuff can conceivably get weird. I
got this in a REPL:
>>> import _md5
>>> _md5.__file__
'/usr/lib/python2.7/lib-dynload/_md5module.so'
Try this on your box and then try putting
_md5 = imp.load_dynamic('_md5', '/usr/lib/python2.7/lib-dynload/_md5module.so')
Or just
import _md5
(with the appropriate path updated to yours) in your code before the offending
line and with some trace statement afterwards. Try the same with _hashlib
instead of _md5 (hashlib defaults to _hashlib which wraps openssl, but if it
doesn't load or doesn't have the needed hash it falls back to _md5, _sha
etc.). If it's not the imports that fail/hang then you can try calling
_md5.new(salt + clear) and _hashlib.openssl_md5(salt + clear) and see if it's
one of them.
If it is the import at fault, then possibly a similar problem was tackled
[here](http://stackoverflow.com/questions/4236045/django-apache-mod-wsgi-
hangs-on-importing-a-python-module-from-so-file) I don't know ejabberd, so I
can't relate their solution to your problem, unfortunately.
I do have to say it, though: in all python implementations I know, = instead
of == in a condition would raise a SyntaxError and that's that - the program
would never even enter the main while loop.
|
Bizzarre issue trying to make Rpy2 2.1.9 work with R 2.12.1, using Python 2.6 under Windows xp - Rpy can't find the R.dll?
Question: I've been having a real issue trying to make Rpy2 play nice with my R install.
I first tried installing the rpy2 MSI package, and this didn't appear to work.
When I ran the recommended tests, it was giving me an error saying that it
couldn't find the R.dll, because the new R installs (post 2.11) install the
DLLs into an i386 folder, where rpy2 can't find them because its looking in
the bin folder instead of the bin/i386 folder.
Then I tried to build the install from scratch myself using the command line
tools (distutils) included with python. This didn't work, because setup.py
claimed to be unable to find the R_home location. But I did work out that
editing an environment variable (PATH) might show the rpy2 setup where to find
the R installation. I then made a couple of edits to the environment, adding
the "R_home" variable pointing to the bin/i386 directory, and made a new entry
under the PATH variable, pointing to the same spot.
Unfortunately, when it found the R path, I got this issue instead:
running build
running build_py
running build_ext
Traceback (most recent call last):
File "setup.py", line 372, in <module>
[os.path.join('doc', 'source', 'rpy2_logo.png')])]
File "C:\Python26\lib\distutils\core.py", line 152, in setup
dist.run_commands()
File "C:\Python26\lib\distutils\dist.py", line 975, in run_commands
self.run_command(cmd)
File "C:\Python26\lib\distutils\dist.py", line 995, in run_command
cmd_obj.run()
File "C:\Python26\lib\distutils\command\build.py", line 134, in run
self.run_command(cmd_name)
File "C:\Python26\lib\distutils\cmd.py", line 333, in run_command
self.distribution.run_command(command)
File "C:\Python26\lib\distutils\dist.py", line 994, in run_command
cmd_obj.ensure_finalized()
File "C:\Python26\lib\distutils\cmd.py", line 117, in ensure_finalized
self.finalize_options()
File "setup.py", line 111, in finalize_options
config += get_rconfig(r_home, about)
File "setup.py", line 264, in get_rconfig
rc = RConfig.from_string(rconfig)
File "setup.py", line 252, in from_string
+ '\nin string\n' + string)
ValueError: Invalid substring in string
So I went back to trying to use the premade install, thinking that maybe the
new edits to the environment might work but got this issue here
Traceback (most recent call last):
File "<string>", line 245, in run_nodebug
File "C:\Documents and Settings\User\Desktop\rpy2-2.1.9\rpy\tests.py", line 3, in <module>
import rpy2.robjects.tests
File "C:\Python26\lib\site-packages\rpy2\robjects\__init__.py", line 12, in <module>
import rpy2.rinterface as rinterface
File "C:\Python26\lib\site-packages\rpy2\rinterface\__init__.py", line 56, in <module>
raise RuntimeError("Unable to locate R.dll within %s" % R_HOME)
RuntimeError: Unable to locate R.dll within C:\Program Files\R\R-2.12.1\bin\i386
This is REALLY weird, because (as anyone can check on their own install) R
installs R.dll into "C:\Program Files\R\R-2.12.1\bin\i386" and I've checked
and verified that its in there, and I've pointed rpy2 to this directory in the
windows default PATH! I know for a fact that rpy2 is looking in the right
place, but can't understand why its not seeing R.dll.
So why can't rpy2 find it? And does anyone know a way to get rpy2 working with
R 2.12? Perhaps I should try the newer rpy2 2.2.0 version? Its still in
development though, and 1.9 is supposed to be able to handle R 2.12 according
to this
[website](http://rpy.sourceforge.net/rpy2/doc-2.2/html/overview.html#requirements)
so I don't know what to do...
Thanks to anyone who can help out...
[EDIT] I've also tried these instructions over [here](http://www.mail-
archive.com/[email protected]/msg02817.html) but they return the
same "can't find DLL" error... Unless you change the environment variable
"R_home" to point straight at the c/program files/R/R 2.12 directory instead
of into the i386 subdirectory.
If it points at the right place, you get these errors back. This looks a bit
more promising... But its still pretty bad!
.......................F....................................F.FFF...F....................................................................F..................................
======================================================================
FAIL: testNewWithoutInit (rpy2.rinterface.tests.test_SexpVector.SexpVectorTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_SexpVector.py", line 43, in testNewWithoutInit
self.assertTrue(False) # worked when tested, but calling endEmbeddedR causes trouble
AssertionError
======================================================================
FAIL: testCallErrorWhenEndedR (rpy2.rinterface.tests.test_EmbeddedR.EmbeddedRTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_EmbeddedR.py", line 122, in testCallErrorWhenEndedR
self.assertTrue(False) # worked when tested, but calling endEmbeddedR causes trouble
AssertionError
======================================================================
FAIL: testReadConsoleWithError (rpy2.rinterface.tests.test_EmbeddedR.EmbeddedRTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_EmbeddedR.py", line 117, in testReadConsoleWithError
self.assertTrue(errorstring.startswith('Traceback'))
AssertionError
======================================================================
FAIL: testSetReadConsole (rpy2.rinterface.tests.test_EmbeddedR.EmbeddedRTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_EmbeddedR.py", line 97, in testSetReadConsole
self.assertEquals(yes.strip(), res[0])
AssertionError: 'yes' != ''
======================================================================
FAIL: testSetWriteConsole (rpy2.rinterface.tests.test_EmbeddedR.EmbeddedRTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_EmbeddedR.py", line 36, in testSetWriteConsole
self.assertEquals('[1] "3"\n', str.join('', buf))
AssertionError: '[1] "3"\n' != ''
======================================================================
FAIL: testWriteConsoleWithError (rpy2.rinterface.tests.test_EmbeddedR.EmbeddedRTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\rinterface\tests\test_EmbeddedR.py", line 55, in testWriteConsoleWithError
self.assertTrue(errorstring.startswith('Traceback'))
AssertionError
======================================================================
FAIL: testVectorUnicodeCharacter (rpy2.robjects.tests.testNumpyConversions.NumpyConversionsTestCase)
----------------------------------------------------------------------
Traceback (most recent call last):
File "C:\Python26\lib\site-packages\rpy2\robjects\tests\testNumpyConversions.py", line 54, in testVectorUnicodeCharacter
self.assertTrue(False) # arrays of unicode characters causing segfault
AssertionError
----------------------------------------------------------------------
Ran 172 tests in 0.407s
FAILED (failures=7)
Exit code: True
Answer: After many hours of searching on the web and trying out many different things,
amongst others encountering the same issues as above, I finally got Rpy2
working on my windows 7 computer!
Basically, the crucial help came from this thread: <http://www.mail-
archive.com/[email protected]/msg03348.html>.
Summarized, these were the steps to get rpy2 up and running on Windows7:
1. Install rpy2 from this link: <https://bitbucket.org/breisfeld/rpy2_w32_fix/issue/1/binary-installer-for-win32>
2. Add the path to R.dll to the environment variable PATH (C:\Program Files\R\R-2.12.1\bin\i386 in my case)
3. Add an environment variable R_HOME (C:\Program Files\R\R-2.12.1 in my case)
4. Add an environment variable R_USER (simply my username in Windows)
5. Restart your Python IDE (otherwise the environment variables are not reloaded!)
|
Restarting a Twisted-python Reactor after an unsuccessful connection
Question: I am writing a server with multiple clients. When a client starts, the server
may not yet be working. So a `reactor.connectTCP` may fail (no receiving end).
Currently I'm solving this by looping on a `reactor.run`, i.e.:
1. connect to server
2. reactor.run
3. if fails, repeat
I understand this is not the way to do it in twisted. How can I do it then?
Answer: You can always try to reconnect within your `connectionLost` handler, for
example:
from twisted.internet.protocol import ClientFactory
class EchoClientFactory(ClientFactory):
def clientConnectionLost(self, connector, reason):
connector.connect()
There is also even a built-in
[`ReconnectingClientFactory`](http://twistedmatrix.com/documents/10.2.0/api/twisted.internet.protocol.ReconnectingClientFactory.html).
See also: this blurb on
[reconnection](http://twistedmatrix.com/documents/current/core/howto/clients.html#auto4).
|
Execute a python script stored on a web server using beautiful soup
Question: I am trying to create a simple form/script combination that will allow someone
to replace the contents of a certain div in an html file with the text they
input in an html form on a separate page.
The script works fine if everything is local : the script is local, i set the
working directory to where my html file is, and i pass the parameter myself
when I run the script. When I load everything to my hosted site server,
however, it gives me a 500 error.
I have been able to execute a simple python script that i stored on my site,
and JustHost, my hosting service, has told me that BeuatifulSoup has been
added to my server.
Here is the script, with the parameter "textcontent" coming from an html form
which works fine. My scirpt is rooted under public_html/cgi-bin/ and the html
I am trying to read and write resides on the root of public_html. I'm guessing
either the html file isn't being found or beautifulsoup isn't actually
available on my server...anyway way to test that??
#!/usr/bin/python
#import beautifulsoup
from BeautifulSoup import BeautifulSoup
# Import modules for CGI handling
import cgi, cgitb, traceback
# Create instance of FieldStorage
try:
form = cgi.FieldStorage()
def text_replace(word):
f = open('/public_html/souptest2.html', 'r')
soup = BeautifulSoup(f.read())
f.close()
text = soup.find('div', attrs={'id': 'sampletext'}).string
text.replaceWith(word)
deploy_html = open('/public_html/souptest2.html', 'w')
deploy_html.write(str(soup))
deploy_html.close()
# Get data from fields
if form.getvalue('textcontent'):
text_content = form.getvalue('textcontent')
text_replace(text_content)
else:
text_content = "Not entered"
except:
deploy_html = open('../souptest2.html', 'w')
traceback.print_exc(deploy_html)
deploy_html.close()
I have tried to load that as a script and run it from a url and still get a
500 error, with no output on my output page in order to debug using
traceback...
Answer: Do you have a shell account on your host? If so, try running the server's
version of Python in interactive mode and type:
>>> import BeautifulSoup
If the module doesn't exist, you should get an `ImportError`.
Alternatively, try putting `cgitb.enable()` immediately following the line
`import cgi, cgitb`. This _should_ give you the traceback of any exceptions
raised. If this _still_ doesn't work, it's likely that your webserver isn't
finding the script. Double-check your configuration with your hosting
provider.
There is a whole bunch of advice on how to debug CGI scripts in Python's CGI
documentation, found [here](http://docs.python.org/library/cgi.html).
**EDIT** : Edited to actually take advantage of the `cgitb` module rather than
try to handroll a solution using `traceback`.
|
Python Classes in 2 Files [Learn Python the Hard Way]
Question: Hey guys, I'm currently completing Zed Shaw's ["Learn Python the Hard
Way"](http://learnpythonthehardway.org/static/LearnPythonTheHardWay.pdf) and
I've been struggling with Exercise 43, which instructs the learner to make a
game. For simplicity, I am attempting to rewrite the previous exercise that
has a class `Game` and some functions:
`__init__`, `play`, `death`, and four more for each "room" in the game.
I was able to copy and modify the code for various conditions, but I wanted to
try to split the code in to two files: one file containing a class
`PrincessRoom` to be the sole room for the game, and the other containing the
bulk of the old code `play` and `death`.
From `ex43.py`
from sys import exit
from random import randint
from ex43princess import PrincessRoom
class Game(object):
def __init__(self, start):
self.quips = [
"You died. You suck.",
"Hey, you died. Look at that.",
"You lose. I win. End.",
]
self.start = start
def play(self):
next = self.start
while True:
print "\n--------"
room = getattr(self, next)
next = room()
def death(self):
print self.quips[randint(0, len(self.quips)-1)]
exit(1)
a_game = Game("princess")
a_game.play()
From `ex43princess.py`
class PrincessRoom(object):
def __init__(self):
pass
def princess(self):
print "text here"
raw_input("> ")
if raw_input == 1:
return 'eat_it'
else:
return 'death'
def eat_it(self):
print "text here"
When I run the code, here's the error I get:
Traceback (most recent call last):
File "ex43-2.py", line 29, in <module>
a_game.play()
File "ex43-2.py", line 21, in play
room = getattr(self, next)
AttributeError: 'Game' object has no attribute 'princess'``
Now I'm not too solid on why the original code had `a_game` initialized with
`a_game = Game("princess")` but I'm pretty sure it's directly related to why
it has me use `room = getattr(self, next)`. But this is where my understanding
falters.
If memory serves, it would appear that `Game` object isn't inheriting properly
from ex43princess.py... right?
If any one could help me understand what is happening here I would be much
appreciative.
Thanks! Josh
Answer: _Note: I'm not familiar with the book and hence with the context of the
question, so my answer refers to the displayed code only_
The problem here isn't splitting the code to two files. As far as I can see,
the `PrincessRoom` class in its own file presents no real problem.
`Game` can't find the `princess` method, and it doesn't have one. Perhaps it
should've inherited from `PrincessRoom`?
That said, I'm not sure that it makes sense logically to inherit a class named
`Game` from a class named `PrincessRoom`. A better approach IMHO would be
_aggregation_ \- i.e. keep a collection of rooms as an instance variable of
`Game` and access them through it. Inheritance should be really reserved to
_is-a_ relations. You should ask yourself, whether "Game is-a PrincessRoom"
makes sense. It probably doesn't. What does make sense is "Game has-a
PrincessRoom", and _has-a_ is represented by aggregation in OOP.
|
Determine if Python script is being executed locally or as CGI
Question: Let's say I have a basic Python script, `test.py`:
#!/usr/bin/python
print "Content-type: text/html\n\n"
print "<html>Hello world!</html>"
How would one determine if the script is being executed locally, e.g.:
python test.py
Or being called via a web browser, e.g. visiting:
http://example.com/test.py
This doesn't seem to be addressed in [the documentation for the `cgi`
module](http://docs.python.org/library/cgi.html). I thought there might be a
difference in the result of `cgi.FieldStorage()` but there doesn't seem to be
one.
The only way I can think to do it is as follows:
#!/usr/bin/python
import os
print "Content-type: text/html\n\n"
print "<html>Hello world!</html>"
if 'REQUEST_METHOD' in os.environ :
print "This is a webpage"
else :
print "This is not a webpage"
Is this the best and/or most ideal method? Why/why not?
Answer: That looks like the best method. There isn't much difference between being
called from the command-line and being started by the web server following a
HTTP request, except for the CGI environment variables, like REQUEST_METHOD.
|
How to set process priority using pywin32 and WMI?
Question:
from win32com.client import GetObject
for proc in GetObject("WinMgmts:{impersonationLevel=impersonate,(IncreaseBasePriority,Debug)}").InstancesOf("Win32_Process"):
if proc.CommandLine == "<my-command-line>":
proc.SetPriority(4) # fails
I have tried passing a _priority class_ (0x40) as well as an actual priority
(4), but both fail with the following message:
File "test.py", line 5, in <module>
proc.SetPriority(0x40)
File "C:\Progs\Python26\lib\site-packages\win32com\client\dynamic.py", line 505, in __getattr__
ret = self._oleobj_.Invoke(retEntry.dispid,0,invoke_type,1)
pywintypes.com_error: (-2147352567, 'Exception occurred.', (0, u'SWbemObjectEx', u'Invalid parameter ', None, 0, -2147217400), None)
I can see that it's not liking some parameter, but why not?
I'm not interested in a non-WMI solution using `SetPriorityClass`. I have
given myself the `SeDebugPrivilege` as follows:
import win32security, ntsecuritycon, win32con, win32api
privs = ((win32security.LookupPrivilegeValue('',ntsecuritycon.SE_DEBUG_NAME), win32con.SE_PRIVILEGE_ENABLED),)
hToken = win32security.OpenProcessToken(win32api.GetCurrentProcess(), win32security.TOKEN_ALL_ACCESS)
win32security.AdjustTokenPrivileges(hToken, False, privs)
win32api.CloseHandle(hToken)
Answer: I encountered the same problem as I was playing with 'GetOwner'.
Just tried this, inspired from WMI:
# using proc as in your code
# this line seems to provide the dispatch interface on the COM object
disp = Dispatch(proc)
# this one gets the method definition
method = disp.Methods_('SetPriority')
# the input parameters, and their description
in_parameters = method.InParameters
in_parameter_names = [(i.Name, i.IsArray) for i in in_parameters.Properties_] \
if not in_parameters is None else [] # not needed here
# >> print in_parameter_names
# [(u'Priority', False)]
# the priority parameter, and setting its value
in_parameters.Properties_['Priority'].Value = 0x40
# doing the call
return_values = disp.ExecMethod_ (method.Name, in_parameters)
For your sample, the following could be skipped. To parse the return values,
just do the same as the inputs:
out_parameters = method.OutParameters
out_parameter_names = [(i.Name, i.IsArray) for i in out_parameters.Properties_] \
if not out_parameters is None else []
res = [return_values.Properties_(i[0]).Value for i in out_parameter_names]
|
Dynamic imports + relative imports in Python 3
Question: I have a **Python 3** project where I'm dynamically importing modules from
disk, using `imp.load_module`. But, I've run into an problem where relative
imports fail, when the relative import occurs within a dynamically imported
module.
From what I've read, I came to the conclusion that only `__file__`,
`__path__`, `__package__`, and `__name__` were used by the default importer
when determining the path of an import. Yet, I've verified these in the code
below, and it still fails when dynamically imported. (It works when imported
in the interpreter with an updated `sys.path`)
# File structure:
# [root]
# ├─ __init__.py
# ├─ board.py
# └─ test.py
****
# Contents of 'board.py':
import os, sys
import root # Already imported... just need a reference
ROOT_DIR = os.path.dirname(root.__file__)
assert root is sys.modules['root']
assert root.__package__ is None
assert root.__name__ == 'root'
assert root.__file__ == os.path.join(ROOT_DIR, '__init__.py')
assert not hasattr(root, '__path__')
xx = object()
assert xx is sys.modules['root.board'].xx
assert __package__ is None
assert __name__ == 'root.board'
assert __file__ == os.path.join(ROOT_DIR, 'board.py')
assert not hasattr(sys.modules['root.board'], '__path__')
assert os.path.isfile(os.path.join(ROOT_DIR, 'test.py'))
from . import test # ImportError('cannot import name test',)
But if I hack `sys.path` and reimport the current package just before the
failed import, it works:
oldroot = root
del sys.modules['root']
sys.path.append(os.path.dirname(ROOT_DIR))
import root
from . import test # No error here
And further, the four golden attributes mentioned above are the same in both
the new and old packages:
assert oldroot.__package__ == root.__package__
assert oldroot.__name__ == root.__name__
assert oldroot.__file__ == root.__file__
assert not hasattr(root, '__path__')
Which means that `__package__`, `__name__`, `__file__`, and `__path__` can't
be the full story. Are there any other attributes that Python uses to locate
imports? What am I overlooking that would cause the import to fail?
Answer: The lack of a `root.__path__` value is suspicious (it means Python doesn't
consider `root` to be a package).
The fact that both `load_module()` calls are being made with a type value of
`1` (a module) instead of the first one having a type of `5` (a package) is
also highly dubious.
Are you using `imp.find_module()` to work out the correct inputs to the
`imp.load_module()` call?
For a package, the input to `imp.load_module()` should look something like
this:
# demo is a package in the current directory for this example
>>> info = imp.find_module('demo')
>>> info
(None, 'demo', ('', '', 5))
>>> demo = imp.load_module('demo', *info)
>>> demo.__path__
['demo']
|
python How to watch for Win32_Processor LoadPercentage change in wmi?
Question: How do I watch for a LoadPercentage change event using the Win32_Processor
class?
import wmi
c= wmi.WMI()
x = [cpu.LoadPercentage for cpu in c.Win32_Processor()]
Where should the watch for() method be applied so that I can know if the CPU
usage has dropped to less than say 80%?
Thanks. Siva
Answer: I don't use that library, but here is an example query:
from win32com.client import Moniker
wmi = Moniker('winmgmts:')
events = wmi.ExecNotificationQuery("Select * From __InstanceModificationEvent "
"Within 1 "
"Where TargetInstance Isa 'Win32_Processor' "
"And TargetInstance.LoadPercentage > 10")
processor = events.NextEvent().TargetInstance
print processor.LoadPercentage
You could also try to use one of the perf WMI classes instead of
Win32_Processor.
|
python object AttributeError: type object 'Track' has no attribute 'title'
Question: I apologize if this is a noob question, but I can't seem to figure this one
out.
I have defined an object that defines a music track (NOTE: originally had the
just ATTRIBUTE vs self.ATTRIBUTE. I edited those values in to help remove
confusion. They had no affect on the problem)
class Track(object):
def __init__(self, title, artist, album, source, dest):
"""
Model of the Track Object
Contains the followign attributes:
'Title', 'Artist', 'Album', 'Source', 'Dest'
"""
self.atrTitle = title
self.atrArtist = artist
self.atrAlbum = album
self.atrSource = source
self.atrDest = dest
I use ObjectListView to create a list of tracks in a specific directory
....other code....
self.aTrack = [Track(sTitle,sArtist,sAlbum,sSource, sDestDir)]
self.TrackOlv.AddObjects(self.aTrack)
....other code....
Now I want to iterate the list and print out a single value of each item
list = self.TrackOlv.GetObjects()
for item in list:
print item.atrTitle
This fails with the error
AttributeError: type object 'Track' has no attribute 'atrTitle'
What really confuses me is if I highlight a single item in the Object List
View display and use the following code, it will correctly print out the
single value for the highlighted item
list = self.TrackOlv.GetSelectedObject()
print list.atrTitle
EDIT: Full source per request. To see error, browse to source dir w/ .mp3
files then click the print button.
#Boa:Frame:Frame1
import wx
import os
import glob
import shutil
import datetime
from mutagen.mp3 import MP3
from mutagen.easyid3 import EasyID3
import mutagen.id3
import unicodedata
from ObjectListView import ObjectListView, ColumnDefn
########################################################################
class Track(object):
def __init__(self, title, artist, album, source, dest):
"""
Model of the Track Object
Contains the followign attributes:
'Title', 'Artist', 'Album', 'Source', 'Dest'
"""
self.atrTitle = title
self.atrArtist = artist
self.atrAlbum = album
self.atrSource = source
self.atrDest = dest
class Action(object):
def __init__(self, timestamp, action, result):
self.timestamp = timestamp
self.action = action
self.result = result
########################################################################
# Non GUI
########################################################################
def selectFolder(sMessage):
print "Select Folder"
dlg = wx.DirDialog(None, message = sMessage)
if dlg.ShowModal() == wx.ID_OK:
# User has selected something, get the path, set the window's title to the path
filename = dlg.GetPath()
else:
filename = "None Selected"
dlg.Destroy()
return filename
def getList(SourceDir):
print "getList"
listOfFiles = None
print "-list set to none"
listOfFiles = glob.glob(SourceDir + '/*.mp3')
return listOfFiles
def getListRecursive(SourceDir):
print "getListRecursive"
listOfFiles = None
listOfFiles = []
print "-list set to none"
for root, dirs, files in os.walk(SourceDir):
for file in files:
if file.endswith(".mp3"):
listOfFiles.append(os.path.join(root,file))
#print listOfFiles
return listOfFiles
def strip_accents(s):
print "strip_accents"
return ''.join((c for c in unicodedata.normalize('NFD', s) if unicodedata.category(c) != 'Mn'))
def replace_all(text):
print "replace_all " + text
dictionary = {'\\':"", '?':"", '/':"", '...':"", ':':"", '&':"and"}
print text
print text.decode('utf-8')
text = strip_accents(text.decode('utf-8'))
for i, j in dictionary.iteritems():
text = text.replace(i,j)
return text
def getTitle(fileName):
print "getTitle"
audio = MP3(fileName)
try:
sTitle = str(audio["TIT2"])
except KeyError:
sTitle = os.path.basename(fileName)
frame.lvActions.Append([datetime.datetime.now(),fileName,"Title tag does not exist, set to filename"])
# TODO: Offer to set title to filename
## If fileName != filename then
## prompt user for action
## Offer Y/n/a
sTitle = replace_all(sTitle)
return sTitle
def getArtist(fileName):
print "get artist"
audio = MP3(fileName)
try:
sArtist = str(audio["TPE1"])
except KeyError:
sArtist = "unkown"
frame.lvActions.Append([datetime.datetime.now(),fileName,"Artist tag does not exist, set to unkown"])
#Replace all special chars that cause dir path errors
sArtist = replace_all(sArtist)
#if name = 'The Beatles' change to 'Beatles, The'
if sArtist.lower().find('the') == 0:
sArtist = sArtist.replace('the ',"")
sArtist = sArtist.replace('The ',"")
sArtist = sArtist + ", The"
return sArtist
def getAblum(fileName):
print "get album"
audio = MP3(fileName)
try:
sAlbum = str(audio["TALB"])
except KeyError:
sAlbum = "unkown"
frame.lvActions.Append([datetime.datetime.now(),fileName,"Album tag does not exist, set to unkown"])
#Replace all special chars that cause dir path error
sAlbum = replace_all(sAlbum)
return sAlbum
########################################################################
# GUI
########################################################################
class MainPanel(wx.Panel):
#----------------------------------------------------------------------
def __init__(self, parent):
wx.Panel.__init__(self, parent=parent, id=wx.ID_ANY)
self.TrackOlv = ObjectListView(self, wx.ID_ANY,
style=wx.LC_REPORT|wx.SUNKEN_BORDER)
self.setTracks()
# Allow the cell values to be edited when double-clicked
self.TrackOlv.cellEditMode = ObjectListView.CELLEDIT_SINGLECLICK
self.ActionsOlv = ObjectListView(self, wx.ID_ANY,
style=wx.LC_REPORT|wx.SUNKEN_BORDER)
self.setActions()
# create browse to source button
sourceBtn = wx.Button(self, wx.ID_ANY, "Browse Source")
sourceBtn.Bind(wx.EVT_BUTTON, self.onBrowseSource)
# create source txt box
self.txSource = wx.TextCtrl(self, wx.ID_ANY, name=u'txSource', value=u'')
# create browse dest button
destBtn = wx.Button(self, wx.ID_ANY, "Browse Destination")
destBtn.Bind(wx.EVT_BUTTON, self.onBrowseDest)
# create dest txt box
self.txDest = wx.TextCtrl(self, wx.ID_ANY, name=u'txDest', value=u'')
# create Move Files button
moveBtn = wx.Button(self, wx.ID_ANY, "Move Files")
moveBtn.Bind(wx.EVT_BUTTON, self.onMoveFiles)
# print list button - debug only
printBtn = wx.Button(self, wx.ID_ANY, "Print List")
printBtn.Bind(wx.EVT_BUTTON, self.onPrintBtn)
# create check box to include all sub files
self.cbSubfolders = wx.CheckBox(self, wx.ID_ANY,
label=u'Include Subfolders', name=u'cbSubfolders', style=0)
self.cbSubfolders.SetValue(True)
self.cbSubfolders.Bind(wx.EVT_CHECKBOX, self.OnCbSubfoldersCheckbox)
# create check box to repace file names
self.cbReplaceFilename = wx.CheckBox(self, wx.ID_ANY,
label=u'Replace Filename with Title Tag',
name=u'cbReplaceFilename', style=0)
self.cbReplaceFilename.SetValue(False)
self.cbReplaceFilename.Bind(wx.EVT_CHECKBOX, self.OnCbReplaceFilenameCheckbox)
# Create some sizers
mainSizer = wx.BoxSizer(wx.VERTICAL)
feedbackSizer = wx.BoxSizer(wx.VERTICAL)
sourceSizer = wx.BoxSizer(wx.HORIZONTAL)
btnSizer = wx.BoxSizer(wx.HORIZONTAL)
feedbackSizer.Add(self.TrackOlv, 1, wx.ALL|wx.EXPAND, 2)
feedbackSizer.Add(self.ActionsOlv, 1, wx.ALL|wx.EXPAND, 2)
sourceSizer.Add(sourceBtn, 0, wx.ALL, 2)
sourceSizer.Add(self.txSource, 1, wx.ALL|wx.EXPAND, 2)
sourceSizer.Add(destBtn, 0, wx.ALL, 2)
sourceSizer.Add(self.txDest, 1, wx.ALL|wx.EXPAND, 2)
btnSizer.Add(printBtn)
btnSizer.Add(moveBtn, 0, wx.ALL, 2)
btnSizer.Add(self.cbSubfolders, 0, wx.ALL, 2)
btnSizer.Add(self.cbReplaceFilename, 0, wx.ALL, 2)
mainSizer.Add(feedbackSizer, 1 , wx.ALL|wx.EXPAND, 2)
mainSizer.Add(sourceSizer, 0, wx.ALL|wx.EXPAND, 2)
#mainSizer.Add(destSizer, 0, wx.ALL|wx.EXPAND, 2)
#mainSizer.Add(destSizer, 0, wx.All|wx.Expand, 2)
mainSizer.Add(btnSizer, 0, wx.ALL, 2)
self.SetSizer(mainSizer)
mainSizer.Fit(self)
#----------------------------------------------------------------------
# Set the GUI column headers and width
#----------------------------------------------------------------------
def setTracks(self, data=None):
self.TrackOlv.SetColumns([
ColumnDefn("Title", "left", 100, "title"),
ColumnDefn("Artist", "left", 100, "artist"),
ColumnDefn("Album", "left", 100, "album"),
ColumnDefn("Source", "left", 300, "source"),
ColumnDefn("Destination", "left", 300, "dest"),
])
def setActions(self, data=None):
self.ActionsOlv.SetColumns([
ColumnDefn("Time", "left", 100, "timestamp"),
ColumnDefn("Action", "left", 450, "action"),
ColumnDefn("Result", "left", 450, "result")
])
#----------------------------------------------------------------------
# GUI EVENTS
#-----------------------------------------------------------------------
EventList = [Action]
#Select Source of files
def onBrowseSource(self, event):
print "OnBrowseSource"
source = selectFolder("Select the Source Directory")
print source
self.txSource.SetValue(source)
self.anEvent = [Action(datetime.datetime.now(),source,"Set as Source dir")]
self.ActionsOlv.AddObjects(self.anEvent)
self.populateList()
#Select Source of files
def onBrowseDest(self, event):
print "OnBrowseDest"
dest = selectFolder("Select the Destination Directory")
print dest
self.txDest.SetValue(dest)
self.anEvent = [Action(datetime.datetime.now(),dest,"Set as Destination dir")]
self.ActionsOlv.AddObjects(self.anEvent)
self.populateList()
def OnCbSubfoldersCheckbox(self, event):
print "cbSubfolder"
self.populateList()
def OnCbReplaceFilenameCheckbox(self, event):
print "cbReplaceFilename"
self.populateList()
def onMoveFiles(self, event):
print "onMoveFiles"
self.moveFiles()
def onPrintBtn(self, event):
print "onPrintBtn"
#Why does this work
#rowObj = self.dataOlv.GetSelectedObject()
#print rowObj.author
#print rowObj.title
#debug - how many item in the list... why does it only print 1?
test = self.TrackOlv.GetItemCount()
print test
print "aphex"
print self.TrackOlv.GetObjects()
for item in xrange(self.TrackOlv.GetItemCount()):
stitle = self.TrackOlv.GetObjectAt(item)
print stitle.atrTitle
#-------------
#Computations
#-------------
def defineDestFilename(self, sFullDestPath):
print "define dest"
iCopyX = 0
bExists = False
sOrigName = sFullDestPath
#If the file does not exist return original path/filename
if os.path.isfile(sFullDestPath) == False:
print "-" + sFullDestPath + " is valid"
return sFullDestPath
#Add .copyX.mp3 to the end of the file and retest until a new filename is found
while bExists == False:
sFullDestPath = sOrigName
iCopyX += 1
sFullDestPath = sFullDestPath + ".copy" + str(iCopyX) + ".mp3"
if os.path.isfile(sFullDestPath) == False:
print "-" + sFullDestPath + " is valid"
self.lvActions.Append([datetime.datetime.now(),"Desitnation filename changed since file exists",sFullDestPath])
bExists = True
#return path/filename.copyX.mp3
return sFullDestPath
def populateList(self):
print "populateList"
sSource = self.txSource.Value
sDest = self.txDest.Value
#Initalize list to reset all values on any option change
self.initialList = [Track]
self.TrackOlv.SetObjects(self.initialList)
#Create list of files
if self.cbSubfolders.Value == True:
listOfFiles = getListRecursive(sSource)
else:
listOfFiles = getList(sSource)
print listOfFiles
#prompt if no files detected
if listOfFiles == []:
self.anEvent = [Action(datetime.datetime.now(),"Parse Source for .MP3 files","No .MP3 files in source directory")]
self.ActionsOlv.AddObjects(self.anEvent)
#Populate list after both Source and Dest are chosen
if len(sDest) > 1 and len(sDest) > 1:
print "-iterate listOfFiles"
for file in listOfFiles:
(sSource,sFilename) = os.path.split(file)
print sSource
print sFilename
#sFilename = os.path.basename(file)
sTitle = getTitle(file)
try:
sArtist = getArtist(file)
except UnicodeDecodeError:
print "unicode"
sArtist = "unkown"
sAlbum = getAblum(file)
# Make path = sDest + Artist + Album
sDestDir = os.path.join (sDest, sArtist)
sDestDir = os.path.join (sDestDir, sAlbum)
#If file exists change destination to *.copyX.mp3
if self.cbReplaceFilename.Value == True:
sDestDir = self.defineDestFilename(os.path.join(sDestDir,sTitle))
else:
sDestDir = self.defineDestFilename(os.path.join(sDestDir,sFilename))
# Populate listview with drive contents
#sSource = self.txSource.Value
sDest = self.txDest.Value
# TODO: Make source = exact source of track, not parent source
# TODO: Seperate dest and filename
self.aTrack = Track(sTitle,sArtist,sAlbum,sSource, sDestDir)
self.TrackOlv.AddObjects(self.aTrack)
self.Update()
#populate list to later use in move command
#self.validatedMove.append([file,sDestDir])
print "-item added to SourceDest list"
else:
print "-list not iterated"
def moveFiles (self):
print "move files"
#for track in self.TrackOlv:
# print "-iterate SourceDest"
# #create dir
# (sDest,filename) = os.path.split(self.TrackOlv)
# print "-check dest"
#
# if not os.path.exists(sDest):
# print "-Created dest"
# os.makedirs(sDest)
# self.lvActions.Append([datetime.datetime.now(),sDest,"Created"])
# self.Update()
# self.lvActions.EnsureVisible(self.lvActions.GetItemCount() -1)
#
# #Move File
# print "-move file"
# shutil.move(SourceDest[0],SourceDest[1])
# self.lvActions.Append([datetime.datetime.now(),filename,"Moved"])
# self.Update()
# self.lvActions.EnsureVisible(self.lvActions.GetItemCount() -1)
#
#self.lvActions.Append([datetime.datetime.now(),"Move Complete","Success"])
#self.Update()
#self.lvActions.EnsureVisible(self.lvActions.GetItemCount() -1)
########################################################################
class MainFrame(wx.Frame):
#----------------------------------------------------------------------
def __init__(self):
wx.Frame.__init__(self, parent=None, id=wx.ID_ANY,
title="MP3 Manager", size=(1024,768)) #W by H
panel = MainPanel(self)
########################################################################
class GenApp(wx.App):
#----------------------------------------------------------------------
def __init__(self, redirect=False, filename=None):
wx.App.__init__(self, redirect, filename)
#----------------------------------------------------------------------
def OnInit(self):
# create frame here
frame = MainFrame()
frame.Show()
return True
#----------------------------------------------------------------------
def main():
"""
Run the demo
"""
app = GenApp()
app.MainLoop()
if __name__ == "__main__":
main()
Answer: You didn't include the bug:
....other code....
self.aTrack = [Track(sTitle,sArtist,sAlbum,sSource, sDestDir)]
self.TrackOlv.AddObjects(self.aTrack)
....other code....
It's somewhere in the first "....other code....", probably on the line where
you first create the self.TrackOlv.
Look at your error message:
AttributeError: type object 'Track' has no attribute 'atrTitle'
It's saying the actual class ("type object 'Track'") is lacking the attribute.
That is, you've added the actual class Track to your list instead of an
instance of that class. It's probably the first item in the list, or your loop
would have printed some titles before throwing the error.
Note the different error messages below:
>>> class Foo(object): pass
...
>>> Foo.cat
Traceback (most recent call last):
File "<input>", line 1, in <module>
AttributeError: type object 'Foo' has no attribute 'cat'
>>> Foo().cat
Traceback (most recent call last):
File "<input>", line 1, in <module>
AttributeError: 'Foo' object has no attribute 'cat'
|
Python: How to update value of key value pair in nested dictionary?
Question: i am trying to make an inversed document index, therefore i need to know from
all unique words in a collection in which doc they occur and how often.
i have used [this](http://stackoverflow.com/questions/651794/whats-the-best-
way-to-initialize-a-dict-of-dicts-in-python/651879#651879) answer in order two
create a nested dictionary. The provided solution works fine, with one problem
though.
First i open the file and make a list of unique words. These unique words i
than want to compare with the original file. When there is a match, the
frequency counter should be updated and its value be stored in the two
dimensional array.
output should eventually look like this:
word1, {doc1 : freq}, {doc2 : freq} <br>
word2, {doc1 : freq}, {doc2 : freq}, {doc3:freq}
etc....
Problem is that i cannot update the dictionary variable. When trying to do so
i get the error:
File "scriptV3.py", line 45, in main
freq = dictionary[keyword][filename] + 1
TypeError: unsupported operand type(s) for +: 'AutoVivification' and 'int'
I think i need to cast in some way the instance of AutoVivification to int....
How to go?
thanks in advance
my code:
#!/usr/bin/env python
# encoding: utf-8
import sys
import os
import re
import glob
import string
import sets
class AutoVivification(dict):
"""Implementation of perl's autovivification feature."""
def __getitem__(self, item):
try:
return dict.__getitem__(self, item)
except KeyError:
value = self[item] = type(self)()
return value
def main():
pad = 'temp/'
dictionary = AutoVivification()
docID = 0
for files in glob.glob( os.path.join(pad, '*.html') ): #for all files in specified folder:
docID = docID + 1
filename = "doc_"+str(docID)
text = open(files, 'r').read() #returns content of file as string
text = extract(text, '<pre>', '</pre>') #call extract function to extract text from within <pre> tags
text = text.lower() #all words to lowercase
exclude = set(string.punctuation) #sets list of all punctuation characters
text = ''.join(char for char in text if char not in exclude) # use created exclude list to remove characters from files
text = text.split() #creates list (array) from string
uniques = set(text) #make list unique (is dat handig? we moeten nog tellen)
for keyword in uniques: #For every unique word do
for word in text: #for every word in doc:
if (word == keyword and dictionary[keyword][filename] is not None): #if there is an occurence of keyword increment counter
freq = dictionary[keyword][filename] #here we fail, cannot cast object instance to integer.
freq = dictionary[keyword][filename] + 1
print(keyword,dictionary[keyword])
else:
dictionary[word][filename] = 1
#extract text between substring 1 and 2
def extract(text, sub1, sub2):
return text.split(sub1, 1)[-1].split(sub2, 1)[0]
if __name__ == '__main__':
main()
Answer: One could use Python's collections.defaultdict instead of creating an
AutoVivification class and then instantiating dictionary as an object of that
type.
import collections
dictionary = collections.defaultdict(lambda: collections.defaultdict(int))
This will create a dictionary of dictionaries with a default value of 0. When
you wish to increment an entry, use:
dictionary[keyword][filename] += 1
|
Python HTTP Server gets multiple requests from iPhone
Question: I created a very basic Python http server (Python v3.2) that uses
BaseHTTPRequestHandler to handle GET requests. It works fine when I use any
web browser on a computer. But, when I use a mobile browser on an iPhone, I
always see three GET requests.
For example, if I run this:
import http.server
from http.server import HTTPServer
from http.server import BaseHTTPRequestHandler
class MyHandler (BaseHTTPRequestHandler):
def do_GET(self):
print(self.path)
print('running server on port 80')
server = HTTPServer(('', 80), MyHandler)
server.serve_forever()
..and then I go to my web browser on my iPhone and enter "192.168.1.191/blah",
the output looks like this:
/blah
/blah
/blah
but if I do it from a computer, it only sends one GET request, so the output
is this:
/blah
Can anyone explain to me why it behaves this way with the iPhone? It
consistently sends 3 requests every single time. Is there any way around this?
By the way, if I use an Apache server, the iPhone does not behave this way. It
only sends one GET request. It's only when I'm using Python to run a server.
Thanks
Answer: Safari returns a request up to three times - obviously in case of _some_ HTTP
error. Generating a proper HTTP response from inside your do_GET() method will
solve this issue.
|
How to create a stock quote fetching app in python
Question: I'm quite new to programming in **Python**.
I want to make an application which will **fetch stock prices** from [google
finance](http://www.google.com/finance). One example is CSCO _(Cisco Sytems)_.
I would then use that data to **warn the user when the stock reaches a certain
value**. It also needs to **refresh every 30 seconds**.
The problem is I dont have a clue how to fetch the data!
Anyone have any ideas?
Answer: This module comes courtesy of [Corey
Goldberg](http://www.goldb.org/goldblog/2007/09/14/PythonStockQuoteModule.aspx).
Program:
import urllib
import re
def get_quote(symbol):
base_url = 'http://finance.google.com/finance?q='
content = urllib.urlopen(base_url + symbol).read()
m = re.search('id="ref_694653_l".*?>(.*?)<', content)
if m:
quote = m.group(1)
else:
quote = 'no quote available for: ' + symbol
return quote
Sample Usage:
import stockquote
print stockquote.get_quote('goog')
**Update** : Changed the regular expression to match Google Finance's latest
format (as of 23-Feb-2011). This demonstrates the main issue when relying upon
screen scraping.
|
Find minimum element in a dictionary of dictionaries
Question: I need to find what element of `apple` has the minimum `size`.
Tnx for all answers. But there is one problem: I use Python 2.4.2 (I can't
change it) and function `min` haven't `key` arg. Yes, I need key of `apple`
apple = {1:{'size':12,'color':'red'},2:{'size':10,'color':'green'}}
Answer:
import operator
min(apple.values(), key=operator.itemgetter('size'))
will return you
{'color': 'green', 'size': 10}
UPDATE: to get the index:
min(apple, key=lambda k: apple[k]['size'])
|
How do I get the x coords to show up after mouse click? - Python
Question: I'm trying to figure out how to get the x coords to show up when the user
clicks a point in the graphics window. Any ideas? Thanks!
Here's my code:
**Set graphics window**
win = GraphWin("Uncle Scrooges Money Bin", 640,480)
win.setCoords(0,0,80,60)
win.setBackground("white")
**Get coordinate of mouse click 1**
point1 = win.getMouse() #*****************************
**Display coordinates of point 1**
print("Point 1 coordinates: ", point1)
Answer: It would be easier to do what you say using `Tkinter` library.
import Tkinter
def mouse(event):
print "Point 1 coordinate :",event.x,event.y
# event parameter will be passed to the function when the mouse is clicked
# This parameter also contains co-ordinates of where the mouse was clicked
# which can be accessed by event.x and event.y
win = Tkinter.Tk() # Main top-level window
win.title("Uncle Scrooges Money Bin")
win.geometry("640x480+80+60") # Set window diensions
frame = Tkinter.Frame(win, background='white', width=640, height=480)
# New frame to handle mouse-clicks
frame.pack() # pack frame(or make frame visible)
frame.bind('<Button-1>', mouse)
# Bind mouse-click event denoted by '<Button-1>' to mouse function
win.mainloop() # Start window main loop
|
Python and FIFOs
Question: I was trying to understand FIFOs using Python under linux and I found a
strange behavior i don't understand.
The following is `fifoserver.py`
import sys
import time
def readline(f):
s = f.readline()
while s == "":
time.sleep(0.0001)
s = f.readline()
return s
while True:
f = open(sys.argv[1], "r")
x = float(readline(f))
g = open(sys.argv[2], "w")
g.write(str(x**2) + "\n")
g.close()
f.close()
sys.stdout.write("Processed " + repr(x) + "\n")
and this is `fifoclient.py`
import sys
import time
def readline(f):
s = f.readline()
while s == "":
time.sleep(0.0001)
s = f.readline()
return s
def req(x):
f = open("input", "w")
f.write(str(x) + "\n")
f.flush()
g = open("output", "r")
result = float(readline(g))
g.close()
f.close()
return result
for i in range(100000):
sys.stdout.write("%i, %s\n" % (i, i*i == req(i)))
I also created two FIFOs using `mkfifo input` and `mkfifo output`.
What I don't understand is why when I run the server (with `python
fifoserver.py input output`) and the client (with `python fifoclient.py`) from
two consoles after some requests the client crashes with a "broken pipe" error
on `f.flush()`. Note that before crashing I've seen from a few hundreds to
several thousands correctly processed requests running fine.
What is the problem in my code?
Answer: As other comments have alluded to, you have a race condition.
I suspect that in the failing case, the server gets suspended after one of
these lines:
g.write(str(x**2) + "\n")
g.close()
The client is then able to read the result, print it to the screen, and loop
back. It then reopens `f` \- which succeeds, because it's still open on the
server side - and writes the message. Meanwhile, the server has managed to
close `f`. Next, the flush on the client side executes a `write()` syscall on
the pipe, which triggers the `SIGPIPE` because it's now closed on the other
side.
If I'm correct, you should be able to fix it by moving the server's
`f.close()` to be above the `g.write(...)`.
|
Is it possible to use variables in PIL (python)?
Question: i'm programing in python 3.1 and using a PIL which are updated for it aswel.
Now it's so that my program is getting info from a webpage and i want this
info to be drawed at a picture which i already got, so i'm using a variable
for this & it's also the part i need help with. What I link is a part of my
program (since it's over 100 lines i'm just showing the parts which i found
realative to the question)
import webbrowser
import random
import urllib.request, urllib.parse, urllib.error
import re
import PIL
from PIL import Image, ImageFont, ImageDraw
arial16 = ImageFont.truetype ("arial.ttf", 16)
Z = (input ("What is the character name? "))
#The link which i get from my input info..
url = "http://"+X+".battle.net/wow/en/character/"+Y+"/"+Z+"/simple"
# Read the webpage
html = urllib.request.urlopen(url).read()
# Encoding
encoding = "utf-8"
html =html.decode (encoding)
# Find right class & choose background from it
cl = re.findall ('class="class">(.*)</a><span class="comma">,</span>', html)
if "Death Knight" : im = Image.open ("DeathKnightBackground.png")
elif "Druid" : im = Image.open ("DruidBackground.png")
elif "Hunter" : im = Image.open ("HunterBackground.png")
elif "Mage" : im = Image.open ("MageBackground.png")
elif "Paladin" : im = Image.open ("PaladinBackground.png")
elif "Priest" : im = Image.open ("PriestBackground.png")
elif "Rogue" : im = Image.open ("RogueBackground.png")
elif "Shaman" : im = Image.open ("ShamanBackground.png")
elif "Warlock" : im = Image.open ("WarlockBackground.png")
elif "Warrior" : im = Image.open ("WarriorBackground.png")
# Find the Title
title = re.findall('<div class="title">(.*)</div>', html)
# If i want to print this i just do
print (("Your Charactername with it's title:")+Z, title)
print (("You are:"),cl)
# Then i want to use a variable to save my picture
S = input("Please enter a name to save your forumsignature: ")
# When i want to draw the text to the picture i tried to use (+Z, title) as in the print
# function - but since this didn't work i will just go with ((+Z, title)) which don't give me
# syntax error
draw = ImageDraw.Draw ( im )
draw.text ( (20,20), ((+ Z, title)), font=arial16, fill="white")
# As i said before, i'm using variable S for saving and tried this way.. but in all the ways i
# have tried, i always keep getting syntax errors
im.save ((+S))
im.show ((+S))
So does anyone know if PIL are able to work with variables in this kind of
way? or does you know some other way to draw text from variables at an image
with python 3.1?
Very cheerful for replies and i will keep trying to test all kind of different
ways i know to get this to work & post up here if i get something to work...
// Zabs
Answer: It is a syntax error. Adding more parenthesis just makes a new datastructure.
Try:
text = Z + " " + title
draw.text ( (20,20), text, font=arial16, fill="white")
and for your save command:
im.save(S)
im.show(S)
|
`python -m unittest discover` does not discover tests
Question: Python's unittest discover does not find my tests!
I have been using nose to discover my unit tests and it is working fine. From
the top level of my project, if I run `nosetests` I get:
Ran 31 tests in 0.390s
Now that python 2.7 [unittest has
discovery](http://docs.python.org/library/unittest.html#unittest-test-
discovery), I have tried using
python -m unittest discover
but I get
Ran 0 tests in 0.000s
My directory structure is:
myproj/
reporter/
__init__.py
report.py
[other app modules]
tests/
__init__.py
test-report.py
[other test modules]
Do you have any ideas why unittest's discovery algorithm can't find the tests?
I'm using Python 2.7.1 and nose 1.0.0 on Windows 7.
Answer: The behaviour is intentional, but the documentation could make this clearer.
If you look at the first paragraph in the test discovery section, it says `For
a project’s tests to be compatible with test discovery they must all be
importable from the top level directory of the project (in other words, they
must all be in Python packages).`
A corollary to that is that the file names must also be valid Python module
names. `test-report.py` fails that test, since `test-report` is not a legal
Python identifier.
A docs bug suggesting that this be mentioned explicitly in the documentation
for the `-p` pattern option would probably be a good way forward.
|
How do I create a radial cluster like the following code-example in Python?
Question: I've found several examples on how to create these exact hierarchies (at least
I believe they are) like the following here
[stackoverflow.com/questions/2982929/](http://stackoverflow.com/questions/2982929/plotting-
results-of-hierarchical-clustering-ontop-of-a-matrix-of-data-in-python) which
work great, and almost perform what I'm looking for.
[EDIT]Here's a simplified version of
[Paul](http://stackoverflow.com/users/31676/paul)'s code, which now should be
easier for someone to help get this into a radial cluster instead of this
current cluster shape
import scipy
import pylab
import scipy.cluster.hierarchy as sch
def fix_verts(ax, orient=1):
for coll in ax.collections:
for pth in coll.get_paths():
vert = pth.vertices
vert[1:3,orient] = scipy.average(vert[1:3,orient])
# Generate random features and distance matrix.
x = scipy.rand(40)
D = scipy.zeros([40,40])
for i in range(40):
for j in range(40):
D[i,j] = abs(x[i] - x[j])
fig = pylab.figure(figsize=(8,8))
# Compute and plot the dendrogram.
ax2 = fig.add_axes([0.3,0.71,0.6,0.2])
Y = sch.linkage(D, method='single')
Z2 = sch.dendrogram(Y)
ax2.set_xticks([])
ax2.set_yticks([])
fix_verts(ax2,0)
fig.savefig('test.png')
But instead of a tree-like structure, I need a radial cluster like the
following diagrams.
 
Answer: I believe you can do this using the `networkx` package in conjunction with
`matplotlib`. Check out the following example from the `networkx` gallery:
<http://networkx.lanl.gov/examples/drawing/circular_tree.html>
In general `networkx` has a number of really nice graph analysis and plotting
methods
|
how to import mysqldb
Question: I have installed MySqldb through .exe(precompiled). Its is stored in site-
packages. But now i don't know how to test, that it is accessable or not. And
major problem how to import in my application like import MySqldb. Help me i
am very new techie in python i just want to work with my existing Mysql.
Thanks in advance...
Answer: Just open your CMD/Console, type `python`, press `Enter`, type `import
MySQLdb` and then press `Enter` again.
If no error is shown, you're ok!
|
Use app engine yaml parser in scripts
Question: I have some configuration files I want to write in yaml and read in a Python
script running on Google app engine. Given that app engine uses app.yaml,
index.yaml among others it seems reasonable to assume there is a python yaml
parser available.
1. How can I gain access to this parser (what is the import) and where can I find its documentation.
2. I'd also like to use this parser for scripts running outside of agg engine (build scripts and such) so how can I gain access to the same import from a script that will run from the command line?
Answer: The YAML library is included with the AppEngine SDK. It is located in
google_appengine/lib/yaml. You should be able to use it in your AppEngine code
just by having `import yaml` in your code.
For non-AppEngine work, a quick Google search reveals <http://pyyaml.org/>
home to many and various Python implementations.
|
.PY into .EXE Python 2.6
Question: I'm trying to convert my .PY script into a .EXE file, in the process I have
tried PY2EXE with the following command line.. `python
C:\Users\Noob\Desktop\setup.py py2exe -p ftplib` -> -p ftplib is for my module
import. When I use this code, I'm left with an .EXE and a bunch of files, if I
take the .EXE out then it will come up with an error. It is required to have
"_socket.pyd" and "python26.dll" or it will crash (the program). How do I
compile this (not having to use PY2EXE or having to use it) without these
extra files? Thanks a lot!
Answer: You should not be taking the exe out of your folder and executing. Just
execute it from the `dist` directory where got created, it has the
python26.dll which the executable needs. If you want to ship it, zip the dist
directory and ship it. Otherwise you have to create an installer using
specific installer software like NSIS. I hope you took a look at the
[Python2.6 specific section](http://www.py2exe.org/index.cgi/Tutorial#Step52),
which has details on how to write data_files to include msvcr90.dll
Also, I am finding this `-p ftplib` cmd option pretty new. Usually all things
to do are within setup.py. Can you point out where this kind of option
specification is mentioned.
|
Django: Cached items not accessible between processes?
Question: I have problems using the django cache. It looks like the cached items are not
readable between processes. Is that by design? I haven't found any information
on it.
Testing on the production server using two ssh sessions in parallel, and
setting the cache in one and reading in the other using the memcache backend
(also tested with file based backend), and this was the result:
(session 1):
>>> from django.core.cache import cache
>>> cache.set('foo','bar')
>>> cache.get('foo')
'bar'
(session 2):
>>> from django.core.cache import cache
>>> cache.get('foo', 0) #Cache has not been set yet...
0
>>> cache.get('foo', 0) #Cache has been set in other session, I expect 'bar' here
0
I use the low level cache api to cache the processed results of an uploaded
file. The user then complete some more steps that describe the uploaded data
at which point it's entered in the DB. This is done asynchronously using
apache2 with one thread per process, mod_wsgi and python 2.5. The problem I
ran in to was that the `"cache.get('<filekey>')"` always returns None when I
test and upload a file.
Thanks
Answer: Django's cache system is an abstraction layer for several different cache
backends. Although it allows you to interact with them using the same API they
will behave differently depending on which one you have configured. See the
[documentation](http://docs.djangoproject.com/en/dev/topics/cache/) for the
full details.
You configure which backend to use using the CACHE_BACKEND setting in your
settings.py file. If you don't set that setting then you'll get a simple, in-
process, cache which would explain why you're not able to access cache values
set in other processes. I would suggest that you look at
[memcached](http://memcached.org/) and use that your backend. It's very fast,
very scalable and also very easy to configure.
|
How to create a tree view with checkboxes in Python
Question: I've been using Tkinter and Tix to write a small program. I'm at a point where
I need a tree view with checkboxes (checkbuttons) so I can select items from
the tree view. Is there an easy way to do this? I've been looking at
ttk.Treeview () and it looks easy to get the tree view but is there a way to
insert a checkbutton to the view?
A simple code snippet would be really appreciated.
I'm not limited to ttk. Anything will do; as long as I have an example or good
docs I can make it work
Answer: 
import Tix
class View(object):
def __init__(self, root):
self.root = root
self.makeCheckList()
def makeCheckList(self):
self.cl = Tix.CheckList(self.root, browsecmd=self.selectItem)
self.cl.pack()
self.cl.hlist.add("CL1", text="checklist1")
self.cl.hlist.add("CL1.Item1", text="subitem1")
self.cl.hlist.add("CL2", text="checklist2")
self.cl.hlist.add("CL2.Item1", text="subitem1")
self.cl.setstatus("CL2", "on")
self.cl.setstatus("CL2.Item1", "on")
self.cl.setstatus("CL1", "off")
self.cl.setstatus("CL1.Item1", "off")
self.cl.autosetmode()
def selectItem(self, item):
print item, self.cl.getstatus(item)
def main():
root = Tix.Tk()
view = View(root)
root.update()
root.mainloop()
if __name__ == '__main__':
main()
|
RSA encryption in .NET, decryption in python
Question: I'm trying to encrypt a short message using RSA algorithm in C# and decrypt
the message using a python skript.
I'd like to use the .NET classes on the C# side and
[pycrypto](http://www.dlitz.net/software/pycrypto/) on python side. I've
managed both sides to use the same key (which was not even trivial since .NET
doesn't support the standard PEM/DER format directly). Encryption/decryption
works on both sides independently.
I'm using PKCS#1 padding on the C# side (setting the `fOAEP` parameter of
`RSACryptoServiceProvider.Encrypt` to `false`), so I'd expect that after
decrypting the block in python I should see some kind of clear text (i.e. my
"message" together with padding bytes)
But all I see is garbage :(.
Are there any caveats/pitfalls I'm not aware of on either side? I'm kind of
out of ideas ...
Thx Martin
**Sample code**
_C# / Encryption_
Console.Write("Input string:");
var s = Console.ReadLine();
var b = Encoding.Default.GetBytes(s);
var encrypted = rsa.Encrypt(b, false);
using (var file = new FileStream(filename, FileMode.Create)) {
file.Write(encrypted, 0, encrypted.Length);
file.Flush();
file.Close();
}
_Python / Decryption_
f = open(filename, "rb")
msg = f.read()
f.close()
decrypted = rsa.decrypt(msg)
print "Decrypted message:"
print_hex(decrypted)
For Key transfer I'm using the `ToXmlString()` method of
`RSACryptoServiceProvider`. The resulting XML is parsed in python and the
_pycrypto_ -RSA object is initialized with
r = Crypto.PublicKey.RSA.construct((modulus, exponent, d, p, q))
where `modulus`, `exponent`, `d`, `p` and `q` are the respective fields of the
.NET-`RSAParameters` structure. (as I've mentioned, I can encrypt/decrypt a
message using this key in python, also `p*q` yields `modulus`, so I think the
key import is working correctly ...)
Answer: Ok, it was my fault, I just didn't look at the results: The leading zero (from
PKCS#1 padding) is not part of the python result string, which looks (in hex)
like:
02 a2 16 4e 51 45 aa 8d
94 b0 de 64 4d 4c 4c bd
0b 01 b8 d2 de dc ed 23
0b 25 c2 11 6c 0a 0b 1f
4f 19 d0 33 18 db e0 81
25 33 f6 e3 70 8d 97 d2
c7 ef 32 ef 27 3c c0 ac
47 68 c0 5b 7b 6d 0d ba
44 da cb bf e8 71 75 d3
2f 9a b1 97 6b 70 4f ff
98 6f 5a 9a 74 3c 65 94
eb 57 52 8a 2f 73 1f 14
7d 76 08 d3 e5 8b 82 b8
5d ed 2b 75 52 29 b5 22
af 76 55 bc 5d e9 41 99
00 4d 61 72 74 69 6e
So, `02` at the beginning points to random padding (somehow I was expecting
0xff padding...). The last 6 bytes (after the zero) are exactly the "Message"
I was expecting, but a normal `print` didn't show them just because of the
zero byte...
|
urlib2.urlopen through proxy fails after a few calls
Question: **Edit:** _after much fiddling, it seems urlgrabber succeeds where urllib2
fails, even when telling it close the connection after each file. Seems like
there might be something wrong with the way urllib2 handles proxies, or with
the way I use it ! Anyways, here is the simplest possible code to retrieve
files in a loop:_
import urlgrabber
for i in range(1, 100):
url = "http://www.iana.org/domains/example/"
urlgrabber.urlgrab(url, proxies={'http':'http://<user>:<password>@<proxy url>:<proxy port>'}, keepalive=1, close_connection=1, throttle=0)
* * *
Hello all !
I am trying to write a very simple python script to grab a bunch of files via
urllib2.
This script needs to work through the proxy at work (my issue does not exist
if grabbing files on the intranet, i.e. without the proxy).
Said script fails after a couple of requests with "HTTPError: HTTP Error 401:
basic auth failed". Any idea why that might be ? It seems the proxy is
rejecting my authentication, but why ? The first couple of urlopen requests
went through correctly !
_Edit: Adding a sleep of 10 seconds between requests to avoid some kind of
throttling that might be done by the proxy did not change the results._
Here is a simplified version of my script (with identified information
stripped, obviously):
import urllib2
passmgr = urllib2.HTTPPasswordMgrWithDefaultRealm()
passmgr.add_password(None, '<proxy url>:<proxy port>', '<my user name>', '<my password>')
authinfo = urllib2.ProxyBasicAuthHandler(passmgr)
proxy_support = urllib2.ProxyHandler({"http" : "<proxy http address>"})
opener = urllib2.build_opener(authinfo, proxy_support)
urllib2.install_opener(opener)
for i in range(100):
with open("e:/tmp/images/tst{}.htm".format(i), "w") as outfile:
f = urllib2.urlopen("http://www.iana.org/domains/example/")
outfile.write(f.read())
Thanks in advance !
Answer: The proxy might be throttling your requests. I guess it thinks you look like a
bot.
You could add a timeout, and see if that gets you through.
|
Asynchronous call into a Synchronous call in Python
Question: In essence I am going to make a call to a remote XMLRPC server and it will
process the request asynchronously.
import xmlrpclib
client = xmlrpclib.ServerProxy('http://localhost:8080')
client.add(3,5)
def add_result(result):
print result
I know at some point in the future that add_result will get called with the
result. The thing is. I want to be able to turn the call client.add into a
blocking call that will return the result. I'm doing this for a GUI that will
be calling on me. The question is where should I be looking to read about this
sort of solution? I'm not really sure where to start.
I don't think I've explained myself well at all. The server I am calling is
implementing the aynchronous part. When I call add it will return true. And I
know that the server is expecting me to implement add_result which is what it
will call on me. What I am trying to do is clean this crazy scheme up so that
someone can call add on me and I will block until add_result is called on me,
I will then return to whoever called me. I hope this clears things up
Answer: Your claim is nonsense. xmlrpclib operations are synchronous and blocking. For
performing asynchrous operations etc. you need to implement something using
threads.
|
Python Convert Lines into a list
Question: I use ifconfig command with awk to catch system's ip addresses
$ ifconfig | grep -E 'inet.[0-9]' | awk '{ print $2}'
127.0.0.1
192.168.8.2
How to convert o/p into a list using python ?
Answer:
import sys
list_of_lines = [line.strip() for line in sys.stdin]
|
Old python hashing done left to right - why is it bad?
Question: I am trying to learn how to defend against security attacks on websites. The
link below shows a good tutorial, but I am puzzled by one statement:
In <http://google-gruyere.appspot.com/part3#3__client_state_manipulation> ,
under "Cookie manipulation", Gruyere says Pythons hash is insecure since it
hashes from left-to-right.
The Gruyere application is using this to encrypt data:
# global cookie_secret; only use positive hash values
h_data = str(hash(cookie_secret + c_data) & 0x7FFFFFF)
c_data is a username; cookie_secret is a static string (which is just '' by
default)
I understand that in more secure hash functions, one change generates a whole
new result, but I don't understand why this insecure, because different c_data
generates whole different hashes!
EDIT: How would one go about beating a hash like this?
Answer: I think that's just a bad explanation there. Python's `hash()` is insecure
because it's easy to find collisions, but "hashes from left to right" has
nothing to do with _why_ it's easy to find collisions. [Cryptographically
secure hashes](http://en.wikipedia.org/wiki/Cryptographic_hash_function) also
process data strictly in sequence; they're likely to operate on data 128 or
256 bits at a time rather than one byte at a time, but that's just a detail of
the implementation.
(It should be said that `hash()` being insecure is _not_ a bug in Python,
because that's not what it's for. It's an exposed detail of the implementation
of Python's dictionaries as [hash
tables](http://en.wikipedia.org/wiki/Hash_table), and you generally _don't_
want a secure hash function for your hash table, because that would slow it
down so much that it would defeat the purpose. Python does provide secure hash
functions in the [hashlib](http://docs.python.org/library/hashlib.html)
module.)
(The use of an insecure hash is not the only problem with the code you show,
but it is by far the most important problem.)
|
multipart/x-mixed-replace ActionScript3 and Google Chrome (and others as well)
Question: I have a strange problem, I'm working on a Bluetooth camera we want to provide
an mjpeg interface to the world.
Mjpeg is just an http server replying one jpeg after the other with the
connection keept open. My server is right now giving me:
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Cache-Directive: no-cache
Expires: 0
Pragma-Directive: no-cache
Server: TwistedWeb/10.0.0
Connection: Keep-Alive
Pragma: no-cache
Cache-Control: no-cache, no-store, must-revalidate;
Date: Sat, 26 Feb 2011 20:29:56 GMT
Content-Type: multipart/x-mixed-replace; boundary=myBOUNDARY
HTTP/1.1 200 OK
Transfer-Encoding: chunked
Cache-Directive: no-cache
Expires: 0
Pragma-Directive: no-cache
Server: TwistedWeb/10.0.0
Connection: Keep-Alive
Pragma: no-cache
Cache-Control: no-cache, no-store, must-revalidate;
Cate: Sat, 26 Feb 2011 20:29:56 GMT
Content-Type: multipart/x-mixed-replace; boundary=myBOUNDARY
And then for each frame:
--myBOUNDARY
Content-Type: image/jpeg
Content-Size: 25992
BINARY JPEG CONTENT.....
(new line)
I made a Flash client for it, so we can use the same code on any device, the
server is implemented in Python using twisted and is targeting Android among
others, problem in Android is Google **forgot** to include mjpeg support....
This client is using URLStream.
The code is this:
package net.aircable {
import flash.errors.*;
import flash.events.*;
import flash.net.URLRequest;
import flash.net.URLRequestMethod;
import flash.net.URLRequestHeader;
import flash.net.URLStream;
import flash.utils.ByteArray;
import flash.utils.Dictionary;
import flash.system.Security;
import mx.utils.Base64Encoder;
import flash.external.ExternalInterface;
import net.aircable.XHRMultipartEvent;
public class XHRMultipart extends EventDispatcher{
private function trc(what: String): void{
//ExternalInterface.call("console.log", what); //for android
trace(what);
}
private var uri: String;
private var username: String;
private var password: String;
private var stream: URLStream;
private var buffer: ByteArray;
private var pending: int;
private var flag: Boolean;
private var type: String;
private var browser: String;
private function connect(): void {
stream = new URLStream();
trc("connect")
var request:URLRequest = new URLRequest(uri);
request.method = URLRequestMethod.POST;
request.contentType = "multipart/x-mixed-replace";
trc(request.contentType)
/* request.requestHeaders = new Array(
new URLRequestHeader("Content-type", "multipart/x-mixed-replace"),
new URLRequestHeader("connection", "keep-alive"),
new URLRequestHeader("keep-alive", "115"));
*/
trace(request.requestHeaders);
trc("request.requestHeaders")
configureListeners();
try {
trc("connecting");
stream.load(request);
trc("connected")
} catch (error:Error){
trc("Unable to load requested resource");
}
this.pending = 0;
this.flag = false;
this.buffer = new ByteArray();
}
public function XHRMultipart(uri: String = null,
username: String = null,
password: String = null){
trc("XHRMultipart()");
var v : String = ExternalInterface.call("function(){return navigator.appVersion+'-'+navigator.appName;}");
trc(v);
v=v.toLowerCase();
if (v.indexOf("chrome") > -1){
browser="chrome";
} else if (v.indexOf("safari") > -1){
browser="safari";
}
else {
browser=null;
}
trc(browser);
if (uri == null)
uri = "../stream?ohhworldIhatethecrap.mjpeg";
this.uri = uri;
connect();
}
private function configureListeners(): void{
stream.addEventListener(Event.COMPLETE, completeHandler, false, 0, true);
stream.addEventListener(HTTPStatusEvent.HTTP_STATUS, httpStatusHandler, false, 0, true);
stream.addEventListener(IOErrorEvent.IO_ERROR, ioErrorHandler, false, 0, true);
stream.addEventListener(Event.OPEN, openHandler, false, 0, true);
stream.addEventListener(ProgressEvent.PROGRESS, progressHandler, false, 0, true);
stream.addEventListener(SecurityErrorEvent.SECURITY_ERROR, securityErrorHandler, false, 0, true);
}
private function propagatePart(out: ByteArray, type: String): void{
trc("found " + out.length + " mime: " + type);
dispatchEvent(new XHRMultipartEvent(XHRMultipartEvent.GOT_DATA, true, false, out));
}
private function readLine(): String {
var out: String = "";
var temp: String;
while (true){
if (stream.bytesAvailable == 0)
break;
temp = stream.readUTFBytes(1);
if (temp == "\n")
break;
out+=temp;
}
return out;
}
private function extractHeader(): void {
var line: String;
var headers: Object = {};
var head: Array;
while ( (line=readLine()) != "" ){
if ( stream.bytesAvailable == 0)
return;
if (line.indexOf('--') > -1){
continue;
}
head = line.split(":");
if (head.length==2){
headers[head[0].toLowerCase()]=head[1];
}
}
pending=int(headers["content-size"]);
type = headers["content-type"];
if ( pending > 0 && type != null)
flag = true;
trc("pending: " + pending + " type: " + type);
}
private function firefoxExtract(): void {
trc("firefoxPrepareToExtract");
if (stream.bytesAvailable == 0){
trc("No more bytes, aborting")
return;
}
while ( flag == false ) {
if (stream.bytesAvailable == 0){
trc("No more bytes, aborting - can't extract headers");
return;
}
extractHeader()
}
trc("so far have: " + stream.bytesAvailable);
trc("we need: " + pending);
if (stream.bytesAvailable =0; x-=1){
buffer.position=x;
buffer.readBytes(temp, 0, 2);
// check if we found end marker
if (temp[0]==0xff && temp[1]==0xd9){
end=x;
break;
}
}
trc("findImageInBuffer, start: " + start + " end: " + end);
if (start >-1 && end > -1){
var output: ByteArray = new ByteArray();
buffer.position=start;
buffer.readBytes(output, 0 , end-start);
propagatePart(output, type);
buffer.position=0; // drop everything
buffer.length=0;
}
}
private function safariExtract(): void {
trc("safariExtract()");
stream.readBytes(buffer, buffer.length);
findImageInBuffer();
}
private function chromeExtract(): void {
trc("chromeExtract()");
stream.readBytes(buffer, buffer.length);
findImageInBuffer();
}
private function extractImage(): void {
trc("extractImage");
if (browser == null){
firefoxExtract();
}
else if (browser == "safari"){
safariExtract();
}
else if (browser == "chrome"){
chromeExtract();
}
}
private function isCompressed():Boolean {
return (stream.readUTFBytes(3) == ZLIB_CODE);
}
private function completeHandler(event:Event):void {
trc("completeHandler: " + event);
//extractImage();
//connect();
}
private function openHandler(event:Event):void {
trc("openHandler: " + event);
}
private function progressHandler(event:ProgressEvent):void {
trc("progressHandler: " + event)
trc("available: " + stream.bytesAvailable);
extractImage();
if (event.type == ProgressEvent.PROGRESS)
if (event.bytesLoaded > 1048576) { //1*1024*1024 bytes = 1MB
trc("transfered " + event.bytesLoaded +" closing")
stream.close();
connect();
}
}
private function securityErrorHandler(event:SecurityErrorEvent):void {
trc("securityErrorHandler: " + event);
}
private function httpStatusHandler(event:HTTPStatusEvent):void {
trc("httpStatusHandler: " + event);
trc("available: " + stream.bytesAvailable);
extractImage();
//connect();
}
private function ioErrorHandler(event:IOErrorEvent):void {
trc("ioErrorHandler: " + event);
}
}
};
The client is working quite well on Firefox where I get all the http header:
--myBOUNDARY
Content-Type: image/jpeg
Content-Size: 25992
So I use content-size to know how many bytes to go ahead. Same happens in IE8
(even buggy IE is compatible!)
On Safari it works a bit differently (maybe it's webkit doing it) I don't get
the http piece just the Binary content, which forces me to search over the
buffer for the start and end of frame.
Problem is Chrome, believe or not, it's not working. Something weird is going
on, apparently I get the first tcp/ip package and then for some reason Chrome
decides to close the connection, the output of the log is this:
XHRMultipart()
5.0 (X11; U; Linux i686; en-US) AppleWebKit/534.16 (KHTML, like Gecko) Chrome/10.0.648.114 Safari/534.16-Netscape
chrome
connect
multipart/x-mixed-replace
request.requestHeaders
connecting
connected
openHandler: [Event type="open" bubbles=false cancelable=false eventPhase=2]
openHandler: [Event type="open" bubbles=false cancelable=false eventPhase=2]
progressHandler: [ProgressEvent type="progress" bubbles=false cancelable=false eventPhase=2 bytesLoaded=3680 bytesTotal=0]
available: 3680
extractImage
chromeExtract()
findImageInBuffer, start: 0 end: -1
httpStatusHandler: [HTTPStatusEvent type="httpStatus" bubbles=false cancelable=false eventPhase=2 status=200 responseURL=null]
available: 0
extractImage
chromeExtract()
findImageInBuffer, start: 0 end: -1
I shouldn't be getting httpStatus until the server closes the connection which
is not the case here.
Please don't tell me to use HTML5 Canvas or Video I all ready been that way,
problem is we want this application to run in many OSes and compiling a video
encoder for all them (ffmpeg for example) will not make the work any easier.
Also we want to provide with SCO audio which is just a PCM stream, so I can't
use plain mjpeg. Canvas is too slow, I tested that, specially on Android.
Answer: Finally I found the problem!
Content-type is wrong according to Chrome's flash plugin, the correct one is:
`Content-Type: multipart/x-mixed-replace`
And not `Content-Type: multipart/x-mixed-replace; boundary=myBOUNDARY`
So my server now sends or not the boundary depending on a request argument.
|
Why is there a handshake failure when trying to run TLS over TLS with this code?
Question: I tried to implement a protocol that can run TLS over TLS using
`twisted.protocols.tls`, an interface to OpenSSL using a memory BIO.
I implemented this as a protocol wrapper that mostly looks like a regular TCP
transport, but which has `startTLS` and `stopTLS` methods for adding and
removing a layer of TLS respectively. This works fine for the first layer of
TLS. It also works fine if I run it over a "native" Twisted TLS transport.
However, if I try to add a second TLS layer using the `startTLS` method
provided by this wrapper, there's immediately a handshake error and the
connection ends up in some unknown unusable state.
The wrapper and the two helpers that let it work looks like this:
from twisted.python.components import proxyForInterface
from twisted.internet.error import ConnectionDone
from twisted.internet.interfaces import ITCPTransport, IProtocol
from twisted.protocols.tls import TLSMemoryBIOFactory, TLSMemoryBIOProtocol
from twisted.protocols.policies import ProtocolWrapper, WrappingFactory
class TransportWithoutDisconnection(proxyForInterface(ITCPTransport)):
"""
A proxy for a normal transport that disables actually closing the connection.
This is necessary so that when TLSMemoryBIOProtocol notices the SSL EOF it
doesn't actually close the underlying connection.
All methods except loseConnection are proxied directly to the real transport.
"""
def loseConnection(self):
pass
class ProtocolWithoutConnectionLost(proxyForInterface(IProtocol)):
"""
A proxy for a normal protocol which captures clean connection shutdown
notification and sends it to the TLS stacking code instead of the protocol.
When TLS is shutdown cleanly, this notification will arrive. Instead of telling
the protocol that the entire connection is gone, the notification is used to
unstack the TLS code in OnionProtocol and hidden from the wrapped protocol. Any
other kind of connection shutdown (SSL handshake error, network hiccups, etc) are
treated as real problems and propagated to the wrapped protocol.
"""
def connectionLost(self, reason):
if reason.check(ConnectionDone):
self.onion._stopped()
else:
super(ProtocolWithoutConnectionLost, self).connectionLost(reason)
class OnionProtocol(ProtocolWrapper):
"""
OnionProtocol is both a transport and a protocol. As a protocol, it can run over
any other ITransport. As a transport, it implements stackable TLS. That is,
whatever application traffic is generated by the protocol running on top of
OnionProtocol can be encapsulated in a TLS conversation. Or, that TLS conversation
can be encapsulated in another TLS conversation. Or **that** TLS conversation can
be encapsulated in yet *another* TLS conversation.
Each layer of TLS can use different connection parameters, such as keys, ciphers,
certificate requirements, etc. At the remote end of this connection, each has to
be decrypted separately, starting at the outermost and working in. OnionProtocol
can do this itself, of course, just as it can encrypt each layer starting with the
innermost.
"""
def makeConnection(self, transport):
self._tlsStack = []
ProtocolWrapper.makeConnection(self, transport)
def startTLS(self, contextFactory, client, bytes=None):
"""
Add a layer of TLS, with SSL parameters defined by the given contextFactory.
If *client* is True, this side of the connection will be an SSL client.
Otherwise it will be an SSL server.
If extra bytes which may be (or almost certainly are) part of the SSL handshake
were received by the protocol running on top of OnionProtocol, they must be
passed here as the **bytes** parameter.
"""
# First, create a wrapper around the application-level protocol
# (wrappedProtocol) which can catch connectionLost and tell this OnionProtocol
# about it. This is necessary to pop from _tlsStack when the outermost TLS
# layer stops.
connLost = ProtocolWithoutConnectionLost(self.wrappedProtocol)
connLost.onion = self
# Construct a new TLS layer, delivering events and application data to the
# wrapper just created.
tlsProtocol = TLSMemoryBIOProtocol(None, connLost, False)
tlsProtocol.factory = TLSMemoryBIOFactory(contextFactory, client, None)
# Push the previous transport and protocol onto the stack so they can be
# retrieved when this new TLS layer stops.
self._tlsStack.append((self.transport, self.wrappedProtocol))
# Create a transport for the new TLS layer to talk to. This is a passthrough
# to the OnionProtocol's current transport, except for capturing loseConnection
# to avoid really closing the underlying connection.
transport = TransportWithoutDisconnection(self.transport)
# Make the new TLS layer the current protocol and transport.
self.wrappedProtocol = self.transport = tlsProtocol
# And connect the new TLS layer to the previous outermost transport.
self.transport.makeConnection(transport)
# If the application accidentally got some bytes from the TLS handshake, deliver
# them to the new TLS layer.
if bytes is not None:
self.wrappedProtocol.dataReceived(bytes)
def stopTLS(self):
"""
Remove a layer of TLS.
"""
# Just tell the current TLS layer to shut down. When it has done so, we'll get
# notification in *_stopped*.
self.transport.loseConnection()
def _stopped(self):
# A TLS layer has completely shut down. Throw it away and move back to the
# TLS layer it was wrapping (or possibly back to the original non-TLS
# transport).
self.transport, self.wrappedProtocol = self._tlsStack.pop()
I have simple client and server programs for exercising this, available from
launchpad (`bzr branch lp:~exarkun/+junk/onion`). When I use it to call the
`startTLS` method above twice, with no intervening call to `stopTLS`, this
OpenSSL error comes up:
OpenSSL.SSL.Error: [('SSL routines', 'SSL23_GET_SERVER_HELLO', 'unknown protocol')]
Why do things go wrong?
Answer: You may need to inform the remote device that you wish to start an environment
and allocate resources for the second layer before you start it up, if that
device has the capabilities.
|
Python subprocess.Popen slow under uWSGI
Question: I've set up a development server running Cherokee on Fedora 14, using uWSGI to
interface with my WSGI application.
When the application is hit with the first request, I spawn a process like so:
from subprocess import Popen
Popen(['bash']) # bash is just an example; the problem happens with all programs
The first request takes 10-15 seconds to complete (subsequent ones take less
than a second). Without the creation of the Popen object, the first request
only takes about 2-3 seconds to complete. When I execute the same Popen
request from a Python shell, it's instantaneous.
What could be causing this behaviour? Have I missed something obvious?
Answer: \--close-on-exec
Otherwise your new process will inherith the socket
(this is a UNIX standard behaviour)
|
Login with python - megaupload
Question: I'm trying to fix a program which can login to my MU account and retrieve some
data....
I don't know what am I doing wrong....That's the code:
#!/usr/bin/env python
import urllib, urllib2, cookielib
username = 'username'
password = 'password'
cj = cookielib.CookieJar()
opener = urllib2.build_opener(urllib2.HTTPCookieProcessor(cj))
login_data = urllib.urlencode({'username' : username, 'password' : password})
opener.open('http://megaupload.com/index.php?c=login', login_data)
resp = opener.open('http://www.megaupload.com/index.php?c=filemanager')
print resp.read()
Thx for any answer!
Answer: You can simulate the filling of the form.
For that you can use [mechanize
lib](http://wwwsearch.sourceforge.net/mechanize/) base on perl module
WWW::Mechanize.
#!/usr/bin/env python
import urllib, urllib2, cookielib, mechanize
username = 'username'
password = 'password'
br = mechanize.Browser()
cj = cookielib.CookieJar()
br.set_cookiejar(cj)
br.set_handle_robots(False)
br.addheaders = [('User-agent', 'Mozilla/5.0 (Windows; U; Windows NT 6.1; fr; rv:1.9.2) Gecko/20100115 Firefox/3.6')]
br.open('http://www.megaupload.com/?c=login')
br.select_form('loginfrm')
br.form['username'] = username
br.form['password'] = password
br.submit()
resp = br.open('http://www.megaupload.com/index.php?c=filemanager')
print resp.read()
See [Use mechanize to log into
megaupload](http://stackoverflow.com/questions/4422389/use-mechanize-to-log-
into-megaupload)
|
Presence autoload in Python 3.x?
Question: Similar feature as:
function __autoload(UndefinedClass)
{
include 'library/'.UndefinedClass.'.php';
}
?>
Python package = _init.py, BIOS=MBR, C++= STIL or templates, PHP5 = autoload,
but python 3.x ?
Answer: No, there is no such feature, because you don't need it. If you want to not
import a module until it's needed, then you just import it when it's needed.
If you want to avoid circular imports, you do pretty much the same thing.
There, now this question has an answer. :-)
|
Computing MD5 checksums for files in a list
Question: I'm working on a bit of a project in Python. I have a list of files that I
want to get the md5checksums for. Then it stores the checksums in another
list. Then it checks again and checks to see if they're different. I have the
function for getting the checksums working but now I can't figure out how I'd
add them to a list. Here is what I'm trying
import sys, hashlib
files = ['/home/file1', '/home/file2', '/home/file3', '/etc/passwd']
md5s = []
def getmd5(file, ex="", inc=""):
m = hashlib.md5()
try:
fd = open(file,"rb")
except IOError:
print "Can't retrieve MD5sum for ", file
pass
content = fd.readlines()
fd.close()
for eachLine in content:
if ex and eachLine.startswith(ex):
continue
m.update(eachLine)
m.update(inc)
a = m.hexdigest()
md5s.append(a)
for i in lists:
getmd5(i)
print md5s
` But when I try this I get 4 lists like so:
['729aebf5b3a841d3ef815e297ae2ce07']
['729aebf5b3a841d3ef815e297ae2ce07', '1c9bc3339234fa7d551bdb8da004c8ad']
['729aebf5b3a841d3ef815e297ae2ce07', '1c9bc3339234fa7d551bdb8da004c8ad', '0c01d98119386db13beb1bfdbae7ba2b']
['729aebf5b3a841d3ef815e297ae2ce07', '1c9bc3339234fa7d551bdb8da004c8ad', '0c01d98119386db13beb1bfdbae7ba2b', 'b51c93a2f965b75de903d159720dd6e6']
`
What I'd like to do is store each hash checksum in the md5s list and then read
to see if they're different.
Answer:
def getmd5(filename, ....):
return m.hexdigest()
md5s = dict()
for fname in filenames:
md5s[fname] = getmd5(fname)
print md5s
|
Some cache problems
Question: 1. I'm wondering if I can delete a cached content made in template cache. I want to delete it from my view. I have in my template `{% cache 500 cache_name sites.number %}` Is it possible to delete all "cache_name" cached content within the view, for example when some action is made?
2. I want to use [per-vie cache](http://docs.djangoproject.com/en/dev//topics/cache/#the-per-view-cache). I do all what is described, but when I call: `@cache_page(3600, cache="cache_name")` I get error:
> Exception Type: ValueError Exception Value: need more than 1 value to unpack
(Below is the traceback)
What I want to achieve is to cache all my template block or view and have a
possibility to delete all cache connected with it when some actions are made.
Pagination is included
**Traceback** :
Environment:
Request Method: GET
Request URL: http://localhost:8000/portfolio/
Django Version: 1.3 beta 1 SVN-15661
Python Version: 2.7.1
Installed Applications:
['django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
'django.contrib.messages',
'django.contrib.staticfiles',
'django.contrib.admin',
'apps.index']
Installed Middleware:
('django.middleware.common.CommonMiddleware',
'django.contrib.sessions.middleware.SessionMiddleware',
'django.middleware.csrf.CsrfViewMiddleware',
'django.contrib.auth.middleware.AuthenticationMiddleware',
'django.contrib.messages.middleware.MessageMiddleware')
Traceback:
File "E:\Python\django\core\handlers\base.py" in get_response
101. request.path_info)
File "E:\Python\django\core\urlresolvers.py" in resolve
252. sub_match = pattern.resolve(new_path)
File "E:\Python\django\core\urlresolvers.py" in resolve
252. sub_match = pattern.resolve(new_path)
File "E:\Python\django\core\urlresolvers.py" in resolve
158. return ResolverMatch(self.callback, args, kwargs, self.name)
File "E:\Python\django\core\urlresolvers.py" in _get_callback
164. self._callback = get_callable(self._callback_str)
File "E:\Python\django\utils\functional.py" in wrapper
124. result = func(*args)
File "E:\Python\django\core\urlresolvers.py" in get_callable
91. lookup_view = getattr(import_module(mod_name), func_name)
File "E:\Python\django\utils\importlib.py" in import_module
35. __import__(name)
File "E:\Python\apps\index\views.py" in <module>
29. @cache_page(600, cache='my_cache')
File "E:\Python\django\views\decorators\cache.py" in cache_page
58. return decorator_from_middleware_with_args(CacheMiddleware)(cache_timeout=args[0], cache_alias=cache_alias, key_prefix=key_prefix)
File "E:\Python\django\utils\decorators.py" in _make_decorator
81. middleware = middleware_class(*m_args, **m_kwargs)
File "E:\Python\django\middleware\cache.py" in __init__
204. self.cache = get_cache(self.cache_alias, **cache_kwargs)
File "E:\Python\django\core\cache\__init__.py" in get_cache
173. backend, location, params = parse_backend_conf(backend, **kwargs)
File "E:\Python\django\core\cache\__init__.py" in parse_backend_conf
131. mod_path, cls_name = backend.rsplit('.', 1)
Exception Type: ValueError at /portfolio/
Exception Value: need more than 1 value to unpack
Answer: What version of Django are you using? The parameter "cache" is only available
in the development version. If you're using Django 1.2, you can only use
"key_prefix".
|
Algorithm to convert unicode to gsm characters
Question: I need an algorithm (preferably in Python) to convert an arbitrary string to a
string containing only characters from the GSM alphabet. I need this filter to
send the string as text in SMS:es. If possible, the algorithm should also
replace characters with their closest encodable equivalent. Examples:
>>> gsm_convert('© all rights reserved')
[copyright sign] all rights reserved
# or
C all rights reserved
>>> gsm_convert('––– long dashes –––')
--- long dashes ---
Python has some builtin algorithms for doing this, but those functions also
convert the input string to ascii which is not correct. GSM handles several
characters not found in ascii.
Answer: From doing this in Perl and PHP I'd do it in two steps using regular
expressions.
* Start by including regular expression support
import re
* Replace any characters you can with their closest match.
I'd suggest using a set of regular expressions for example replace "á" with
"a" using the following
message = ur'abc\u00e9\u00e1'
message = re.sub(ur'\u00e1','a',message)
* Remove any remaining characters that aren't in the GSM character set.
message = ur'abc\u00e9\u00e1'
message = re.sub(ur'[^\u0040\u00A3\u0024\u00A5\u00E8\u00E9\u00F9\u00EC\u00F2\u00C7\u000A\u00D8\u00F8\u000D\u00C5\u00E5\u0394\u005F\u03A6\u0393\u039B\u03A9\u03A0\u03A8\u03A3\u0398\u039E\u00C6\u00E6\u00DF\u00C9\u0020\u0021\u0022\u0023\u00A4\u0025\u0026\u0027\u0028\u0029\u002A\u002B\u002C\u002D\u002E\u002F\u0030\u0031\u0032\u0033\u0034\u0035\u0036\u0037\u0038\u0039\u003A\u003B\u003C\u003D\u003E\u003F\u00A1\u0041\u0042\u0043\u0044\u0045\u0046\u0047\u0048\u0049\u004A\u004B\u004C\u004D\u004E\u004F\u0050\u0051\u0052\u0053\u0054\u0055\u0056\u0057\u0058\u0059\u005A\u00C4\u00D6\u00D1\u00DC\u00A7\u00BF\u0061\u0062\u0063\u0064\u0065\u0066\u0067\u0068\u0069\u006A\u006B\u006C\u006D\u006E\u006F\u0070\u0071\u0072\u0073\u0074\u0075\u0076\u0077\u0078\u0079\u007A\u00E4\u00F6\u00F1\u00FC\u00E0\u20AC\u005B\u005C\u005D\u005E\u007B\u007C\u007D\u007E]','',message)
print message
In this example it will print `abcé`, removing the `á` (`\u00e1`) which isn't
part of the GSM character set.
|
Python: Mock a module without importing it or needing it to exist
Question: I am using starting to use a python [mock
library](http://www.voidspace.org.uk/python/mock/index.html) for my testing. I
want to mock a module that is imported within the namespace of the module
under test without actually importing it or requiring that it exist first
(i.e. throwing an ImportError).
Suppose the following code exists:
foo.py
import helpers
def foo_func():
return helpers.helper_func()
The goal is to test foo_func() when 'helpers.py' does not exist anywhere, and
if it does exist, act as if it doesn't.
First try, using the super cool @patch decorator:
from mock import patch, sentinel
import foo
@patch("foo.helpers")
def foo_test(mock):
mock.helper_func.return_value = sentinel.foobar
assert foo.foo_func() == sentinel.foobar
This works if the "helpers" module can be imported. If it doesn't exist, I get
an ImportError.
Next attempt with patch, sans decorator:
from mock import patch, sentinel, Mock
import foo
helpers_mock = patch("foo.helpers")
helpers_mock.start()
def foo_test():
helpers_mock.helper_func = Mock('helper_func')
helpers_mock.helper_func.return_value = sentinel.foobar
assert foo.foo_func() == sentinel.foobar
Again, this doesn't work if "helpers" is missing... and, if it exists, the
assertion fails. Not really sure why that happens.
Third attempt, current solution:
import sys
helpers_mock = Mock(name="helpers_mock", spec=['helper_func'])
helpers_mock.__name__ = 'helpers'
sys.modules['helpers'] = helpers_mock
import foo
def foo_test():
helpers_mock.helper_func.return_value = sentinel.foobar
assert foo.foo_func() == sentinel.foobar
This test passes regardless of whether or not "helpers.py" exists.
Is this the best way to accomplish this goal? Does the mocking library I am
using provide an alternative to this? What other ways can I do this?
Answer: You're kind of missing the point of what a Mock is. You're supposed to build
them when you want an object with a particular interface, regardless of how
it's implemented.
What you're doing is trying to re-implement python's module system, plus it's
a pretty horrible abuse of global variables to boot.
Instead of making foo a module, make a Foo class, and pass in the helpers in
the constructor.
class Foo(object):
def __init__(self, helpers):
self.helpers = helpers
# then, instead of import foo:
foo = Foo(mock_helpers)
Even if the real "helpers" is actually going to be a module, there is no
reason you need to be messing with sys.modules and setting it up via `import`
in your tests.
And if foo has to be a module, that's fine too, but you do it like this:
# foo.py
class Foo(object):
pass # same code as before, plus foo_func
try:
import whatever
_singleton = Foo(whatever)
except ImportError:
_singleton = Foo(something_else)
def foo_func():
return _singleton.foo_func()
Large chunks of the standard library work this way. It's pretty much the
standard for defining singleton-like modules.
|
python subprocess.popen get into an infinite loop
Question: I'm trying to run the folowing command on a sub process and collecting the
output.
nmap -n -PN -sT -T4 -p 445,139 10.11.1.0/24 --exclude matrix
this command return an error which is fine by me.
The problem is when i'm doing this from python like this:
import subprocess
nmap_process = subprocess.Popen(command, stdout=subprocess.PIPE,stderr=subprocess.PIPE)
output,errOutput=nmap_process.communicate()
the process hang.
if i don't use the stderr param,the first error line of namp is printed in an
infinite loop
does anybody have any segesstion about how to handle this?
Answer:
import subprocess
cmd = "nmap -n -PN -sT -T4 -p 445,139 10.11.1.0/24 --exclude matrix"
pro = subprocess.Popen(cmd, stdout = subprocess.PIPE, stderr = subprocess.PIPE)
pro.communicate() #[0] is stdout [1] is stderr :P
self.nmap_process.communicate() seems to be your problem. Are you creating
this inside a class? Can we see more of the code? Also when I run a nmap
stderr cmd in the same code I don't get a hang in my code, and It doesn't
infinite loop.
|
wxpython: nested sizers, and little square in top left corner?
Question: I'm trying to look into wxPython and sizers, and I put together the following
example:
import wx
class MyTestFrame(wx.Frame):
def __init__(self, parent, title):
super(MyTestFrame, self).__init__(parent, title=title,
size=(250, 150))
# the master panel of the frame - "Add a panel so it looks correct on all platforms"
self.panel = wx.Panel(self, wx.ID_ANY)
# self.panel.SetBackgroundColour(wx.Colour(124, 224, 124)) # to confirm the square is the panel
# want these buttons absolutely positioned
btn_A = wx.Button(self, id=1, label='A', pos=(10, 10), size=(30, 30))
btn_A.SetBackgroundColour(wx.Colour(224, 124, 124))
btn_B = wx.Button(self, id=2, label='B', pos=(45, 10), size=(30, 30))
btn_C = wx.Button(self, id=3, label='C', pos=(80, 10), size=(30, 30))
# additional object
mastersizer = wx.BoxSizer(wx.VERTICAL)
btnsizer = wx.BoxSizer(wx.HORIZONTAL)
btnsizer.Add(btn_A, 0)
btnsizer.Add(btn_B, 0)
btnsizer.Add(btn_C, 0)
mastersizer.Add(btnsizer, 1, wx.EXPAND)
self.panel.SetSizer(mastersizer)
#~ mastersizer.Fit(self) # makes the window as large as the buttons
self.Centre()
self.Show()
if __name__ == '__main__':
app = wx.App()
MyTestFrame(None, 'Test')
app.MainLoop()
When I run this, I get a window like on the image:
Can someone explain, why do I get that gray little square in the upper left
corner - and what would be the correct way to implement the code? (The button
is deliberately colored, so it can be obvious.. ) I'm on Ubuntu Lucid, in case
this is platform specific.
EDIT: That square is apparently the panel itself, but then I cannot tell why
doesn't it resize and become the 'parent' for the buttons, as intended?
Answer: Ah well - wasn't that bad; but wasn't that obvious to me :) So here's some
reference for other noobs like myself: In the above code, the buttons are
defined as children of the frame - not of the panel; so the only change is
this:
# want these buttons absolutely positioned
# must be children of panel - if panel is to encompass them!
btn_A = wx.Button(self.panel, id=1, label='A', pos=(10, 10), size=(30, 30))
btn_A.SetBackgroundColour(wx.Colour(224, 124, 124))
btn_B = wx.Button(self.panel, id=2, label='B', pos=(45, 10), size=(30, 30))
btn_C = wx.Button(self.panel, id=3, label='C', pos=(80, 10), size=(30, 30))
And then all seems fine:
Well, sorry to have wasted space here - but hopefully, may be of use to others
:)
Cheers!
|
Python: get datetime for '3 years ago today'?
Question: This must be a duplicate (and documented), but I can't find the answer via
Google.
In Python, how do I get a datetime object for '3 years ago today'?
Thanks!
UPDATE: FWIW, I don't care hugely about accuracy... i.e. it's Feb 29th today,
I don't care whether I'm given Feb 28th or March 1st in my answer. Concision
is more important than configurability, in this case.
Answer: If you need to be exact use the
[dateutil](https://pypi.python.org/pypi/python-dateutil/2.1) module to
calculate relative dates
from datetime import datetime
from dateutil.relativedelta import relativedelta
three_yrs_ago = datetime.now() - relativedelta(years=3)
|
Extending c functionality of PIL
Question: I want to create functionality similar to PIL's `Image.blend`, using a
different blending algorithm. To do this would I need to: (1) directly modify
the PIL modules and compile my own custom PIL or (2) write a python c module
which imports and extends PIL?
I have unsuccessfully tried:
#include "_imaging.c"
I also was trying to just pull out the parts I need from the PIL source and
put them in my own file. The farther I got in the more things I had to pull
and it seems that is not the ideal solution.
**UPDATE:** edited to add the blending algorithm implemented in python (this
emulates the overlay blending mode in Photoshop):
def overlay(upx, lpx):
return (2 * upx * lpx / 255 ) if lpx < 128 else ((255-2 * (255 - upx) * (255 - lpx) / 255))
def blend_images(upper = None, lower = None):
upixels = upper.load()
lpixels = lower.load()
width, height = upper.size
pixeldata = [0] * len(upixels[0, 0])
for x in range(width):
for y in range(height):
# the next for loop is to deal with images of any number of bands
for i in range(len(upixels[x,y])):
pixeldata[i] = overlay(upixels[x, y][i], lpixels[x, y][i])
upixels[x,y] = tuple(pixeldata)
return upper
I have also unsuccessfully tried implementing this using scipy's
`weave.inline`:
def blend_images(upper=None, lower=None):
upixels = numpy.array(upper)
lpixels = numpy.array(lower)
width, height = upper.size
nbands = len(upixels[0,0])
code = """
#line 120 "laplace.py" (This is only useful for debugging)
int upx, lpx;
for (int i = 0; i < width-1; ++i) {
for (int j=0; j<height-1; ++j) {
for (int k = 0; k < nbands-1; ++k){
upx = upixels[i,j][k];
lpx = lpixels[i,j][k];
upixels[i,j][k] = ((lpx < 128) ? (2 * upx * lpx / 255):(255 - 2 * (255 - upx) * (255 - lpx) / 255));
}
}
}
return_val = upixels;
"""
# compiler keyword only needed on windows with MSVC installed
upixels = weave.inline(code,
['upixels', 'lpixels', 'width', 'height', 'nbands'],
type_converters=converters.blitz,
compiler = 'gcc')
return Image.fromarray(upixels)
I'm doing something wrong with the `upixel` and `lpixel` arrays but I'm not
sure how to fix them. I'm a bit confused about the type of `upixels[i,j][k]`,
and not sure what I could assign it to.
Answer: Here's my implementation in [NumPy](http://numpy.scipy.org/). I have no unit
tests, so I do not know if it contains bugs. I assume I'll hear from you if it
fails. Explanation of what is going on is in the comments. It processes a
200x400 RGBA image in 0.07 seconds
import Image, numpy
def blend_images(upper=None, lower=None):
# convert to arrays
upx = numpy.asarray(upper).astype('uint16')
lpx = numpy.asarray(lower).astype('uint16')
# do some error-checking
assert upper.mode==lower.mode
assert upx.shape==lpx.shape
# calculate the results of the two conditions
cond1 = 2 * upx * lpx / 255
cond2 = 255 - 2 * (255 - upx) * (255 - lpx) / 255
# make a new array that is defined by condition 2
arr = cond2
# this is a boolean array that defines where in the array lpx<128
mask = lpx<128
# populate the parts of the new arry that meet the critera for condition 1
arr[mask] = cond1[mask]
# prevent overflow (may not be necessary)
arr.clip(0, 255, arr)
# convert back to image
return Image.fromarray(arr.astype('uint8'), upper.mode)
|
MAC Address from IP across network
Question: I hope you're all well.
I'm wondering if you could help me or point me in the right direction. I'm
currently working on a project that centers around network management. Due to
severe time constraints where possible I'm using opensource code. The issue
I'm having is that part of the project requires me to be able to capture the
MAC addresses of all of the devices that are connected to the network.
My knowledge of network orientated programming is limited as I have been
working in other areas of software engineering for the past 4 years. The
approach I have taken is to use nmap as a basis to get the ip address and
other information I need. The MAC address is not included in the nmap out put
and from what I have read it seems to be a bit flakey. (i could be wrong).
Therefore I have tried to do this in a two stage approach, firstly I get the
data including ip address from nmap which works fine. My next step and the bit
I'm having difficulty with is I ping the ip address (from within my python
program) which works. But how do I get the MAC Address from the IP address? I
initially thought ping the ip and grab the MAC from the ARP but I think that
will only work if the IP address is on the same subnet. to compound the
problem on deployment there could be up to 5000 computers on the network that
needs to be logged. To show you my python ping approach this is the code:
import pdb, os
import subprocess
import re
from subprocess import Popen, PIPE
# This will only work within the netmask of the machine the program is running on cross router MACs will be lost
ip ="192.168.0.4"
#PING to place target into system's ARP cache
process = subprocess.Popen(["ping", "-c","4", ip], stdout=subprocess.PIPE)
process.wait()
result = process.stdout.read()
print(result)
#MAC address from IP
pid = Popen(["arp", "-n", ip], stdout=PIPE)
s = pid.communicate()[0]
# [a-fA-F0-9] = find any character A-F, upper and lower case, as well as any number
# [a-fA-F0-9]{2} = find that twice in a row
# [a-fA-F0-9]{2}[:|\-] = followed by either a ?:? or a ?-? character (the backslash escapes the hyphen, since the # hyphen itself is a valid metacharacter for that type of expression; this tells the regex to look for the hyphen character, and ignore its role as an operator in this piece of the expression)
# [a-fA-F0-9]{2}[:|\-]? = make that final ?:? or ?-? character optional; since the last pair of characters won't be followed by anything, and we want them to be included, too; that's a chunk of 2 or 3 characters, so far
# ([a-fA-F0-9]{2}[:|\-]?){6} = find this type of chunk 6 times in a row
mac = re.search(r"([a-fA-F0-9]{2}[:|\-]?){6}", s).groups()[0] #LINUX VERSION ARP
mac = re.search(r"(([a-f\d]{1,2}\:){5}[a-f\d]{1,2})", s).groups()[0] #MAC VERSION ARP
print(mac)
I have looked for some information but what I have found seems a bit vague. If
you know of any ideas or avenues of research that may help me I would be
greatful
Cheers
Chris
Answer: You can't directly get the MAC address of a machine outside your subnet.
A common strategy for network management applications is to query machines
that _do_ have this information, such as the routers and switches connecting
the machines, using [SNMP](http://en.wikipedia.org/wiki/Snmp). Routers have
arp tables for the subnets to which they are directly connected (as they need
this to do their job), and this information can be acquired from the router.
The answers to [this question](http://stackoverflow.com/questions/156853/what-
is-the-best-snmp-implementation-for-python) might help with finding python
library code to help in this endeavor.
|
python script execution through crontab
Question: what happens to my script in python that does not run through crontab every
minute. My script has execute permissions and then calls two other scripts in
python.
This is the content of my crontab (#crontab -l):
*/1 * * * * /usr/bin/rsm/samplesMonitor.py
` Thank you guys.
Answer: Check `/var/log/syslog` for errors.
DIAGNOSTICS
cron requires that each entry in a crontab end in a
newline character. If the last entry in a crontab is
missing a newline (ie, terminated by EOF), cron will
consider the crontab (at least partially) broken. A
warning will be written to syslog.
* * *
**Update:** According to your log message, the script is running but returning
an error code. Cron will email you the output, if you have a mail agent
installed.
Try either:
1. install a mail agent, such as: `apt-get install exim4`
2. change your cron line to log to file, like so:
* * * * * /usr/bin/rsm/samplesMonitor.py 2>&1 >> /tmp/script.log
* * *
**Update 2:** I re-read your question and it acurred to me that maybe you are
running into python import issues. You say that your script calls two other
scripts. My suggestion would be to test running your script from `/`. Python
has a default behavior to find imports in the current working directory, so
make sure your script can run from any path location.
In the crontab, you can set the starting working directory by calling your
script from within another shell process. For example:
bash -c "cd THE_WORKING_DIR;/usr/bin/rsm/samplesMonitor.py"
|
How does sleekxmpp components work?
Question: This may sound dumb but I followed this tutorial:
<https://github.com/fritzy/SleekXMPP/wiki/Creating-a-SleekXMPP-Plugin>
and here's the component at the end that uses the XEP-0077 plugin that was
created:
import sleekxmpp.componentxmpp
class Example(sleekxmpp.componentxmpp.ComponentXMPP):
def __init__(self, jid, password):
sleekxmpp.componentxmpp.ComponentXMPP.__init__(self, jid, password, 'localhost', 8888)
self.registerPlugin('xep_0030')
self.registerPlugin('xep_0077')
self.plugin['xep_0077'].setForm('username', 'password')
self.add_event_handler("registered_user", self.reg)
self.add_event_handler("unregistered_user", self.unreg)
def reg(self, iq):
msg = "Welcome! %s" % iq['register']['username']
self.sendMessage(iq['from'], msg, mfrom=self.fulljid)
def unreg(self, iq):
msg = "Bye! %s" % iq['register']['username']
self.sendMessage(iq['from'], msg, mfrom=self.fulljid)
But I don't know how to use it, also I can't find any sleekxmpp documentation
how to use this component. What I'm trying to accomplish here is to be able to
register/unregister users on an xmpp server from python.
Answer: Check out
<http://louizatakk.fedorapeople.org/sleekxmpp-1.0-Beta2-0/examples/config_component.py>
It will answer all of your questions. If not, post a comment with with the
follow-up questions below.
|
How to turn off blinking cursor in command window?
Question: I have a Python script that sends output to a DOS command window (I am using
Windows 7) using the print() function, but I would like to prevent (or hide)
the cursor from blinking at the next available output position. Has anyone any
idea how I can do this? I have looked at a list of DOS commands but I cannot
find anything suitable.
Any help would be appreciated. Alan
Answer: I've been writing a cross platform colour library to use in conjunction with
Colorama (http://pypi.python.org/pypi/colorama) for Python 3. To totally hide
the cursor on windows or linux:
import sys
import os
if os.name == 'nt':
import msvcrt
import ctypes
class _CursorInfo(ctypes.Structure):
_fields_ = [("size", ctypes.c_int),
("visible", ctypes.c_byte)]
def hide_cursor():
if os.name == 'nt':
ci = _CursorInfo()
handle = ctypes.windll.kernel32.GetStdHandle(-11)
ctypes.windll.kernel32.GetConsoleCursorInfo(handle, ctypes.byref(ci))
ci.visible = False
ctypes.windll.kernel32.SetConsoleCursorInfo(handle, ctypes.byref(ci))
elif os.name == 'posix':
sys.stdout.write("\033[?25l")
sys.stdout.flush()
def show_cursor():
if os.name == 'nt':
ci = _CursorInfo()
handle = ctypes.windll.kernel32.GetStdHandle(-11)
ctypes.windll.kernel32.GetConsoleCursorInfo(handle, ctypes.byref(ci))
ci.visible = True
ctypes.windll.kernel32.SetConsoleCursorInfo(handle, ctypes.byref(ci))
elif os.name == 'posix':
sys.stdout.write("\033[?25h")
sys.stdout.flush()
The above is a selective copy & paste. From here you should pretty much be
able to do what you want. Assuming I didn't mess up the copy and paste this
was tested under Windows Vista and Linux / Konsole.
|
Is there any working example of "pytap" TAP emitter for Python
Question: if we look at like in example 3:
#TEST SOME STUFF
from TAP.Simple import *
plan(3)
def in_between(value, bottom, top, msg):
ret = ok(((bottom = value) and (value = top)), msg)
if (not ret):
diag("value %s is not between %s and %s" % (value, bottom, top))
return ret
in_between(5, 3, 10, "5 is OK.")
in_between(5.5, 5, 6, "5[2] is OK.")
# This will fail.
in_between(1, 20, 30, "1 is in range.")
I am trying to see how i can use this with real Python code
note: the ret = ok statement has <= and => instead of just = , the code was
not getting displayed so i took them out, and i am not sure how to escape them
Here is an example that can be used as a source.
'''Convert to and from Roman numerals
This program is part of 'Dive Into Python 3', a free Python book for
experienced programmers. Visit http://diveintopython3.ep.io/ for the
latest version. - old website http://diveintopython3.org/ is not available anymore.
'''
roman_numeral_map = (('M', 1000),
('CM', 900),
('D', 500),
('CD', 400),
('C', 100),
('XC', 90),
('L', 50),
('XL', 40),
('X', 10),
('IX', 9),
('V', 5),
('IV', 4),
('I', 1))
def to_roman(n):
'''convert integer to Roman numeral'''
result = ''
for numeral, integer in roman_numeral_map:
while n >= integer:
result += numeral
n -= integer
return result
# Copyright (c) 2009, Mark Pilgrim, All rights reserved.
#
# Redistribution and use in source and binary forms, with or without modification,
# are permitted provided that the following conditions are met:
#
# * Redistributions of source code must retain the above copyright notice,
# this list of conditions and the following disclaimer.
# * Redistributions in binary form must reproduce the above copyright notice,
# this list of conditions and the following disclaimer in the documentation
# and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 'AS IS'
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
# POSSIBILITY OF SUCH DAMAGE.
Answer: OK , i figured it out myself, by looking at perl's TAP examples, and
transposing it to fit Python
#!/usr/bin/env python
import TAP
ok = TAP.Builder.create(3).ok
def hello_world():
return "Hello, World!"
ok(hello_world() == "Hello, World!", "First Test")
ok(hello_world() is "Hello, World!", "Second Test")
ok(isinstance(hello_world(),str), "Third Test")
Explanation:
1. `import TAP` once you have installed it on your host
2. `ok = TAP.Builder.create(3).ok`: 3 means you plan 3 tests, the rest just follow without questions
3. First Test uses "code" then condition (`==`) and then expected result
The same goes for `is`, or `isinstance()`
|
Scanning for thread violations with Tkinter
Question: We are just about to finish a very large update to our application which is
built with python2.5 and Tkinter and the following error has crept in sadly:
alloc: invalid block: 06807CE7: 1 0 0
This application has requested the Runtime to terminate it in an unusual way.
Please contact the application's support team for more information.
We've seen this before and it is usually a Tcl Interrupter error caused when a
non GUI thread tries to access TK via Tkinter in anyway (TK not being thread
safe). The error pops up on application close, after the python interrupter is
finished with our code. This error is very hard to reproduce and I'm thinking
I will have to scan all threads in the system to see if they access TK when
they shouldn't.
I'm looking for a magic python trick to help with this. All Tkinter widgets we
use are first subclassed and inherit from out own Widget base class.
With this in mind I'm looking for a way to add the following check to the
beginning of every method in the widget sub classes:
import thread
if thread.get_ident() != TKINTER_GUI_THREAD_ID:
assert 0, "Invalid thread accessing Tkinter!"
Decorators as a partial solution comes to mind. I do not want to add
decorators manually to each method however. Is there a way I can add the
decorator to all methods of a class that inherits from our Widget base class?
Or is there a better way to do all this? Or does anyone have more info about
this error?
enter code here
Answer: I don't know if your approach is good, as I don't know Tkinter.
But here's a sample of how to decorate all class methods using a metaclass.
import functools
# This is the decorator
def my_decorator(func):
@functools.wraps(func)
def wrapper(*args, **kwargs):
print 'calling', func.__name__, 'from decorator'
return func(*args, **kwargs)
return wrapper
# This is the metaclass
class DecorateMeta(type):
def __new__(cls, name, bases, attrs):
for key in attrs:
# Skip special methods, e.g. __init__
if not key.startswith('__') and callable(attrs[key]):
attrs[key] = my_decorator(attrs[key])
return super(DecorateMeta, cls).__new__(cls, name, bases, attrs)
# This is a sample class that uses the metaclass
class MyClass(object):
__metaclass__ = DecorateMeta
def __init__(self):
print 'in __init__()'
def test(self):
print 'in test()'
obj = MyClass()
obj.test()
The metaclass overrides the class creation. It loops through all the
attributes of the class being created and decorates all callable attributes
that have a "regular" name with `my_decorator`.
|
Correct Regexp for japanese sentence tokenizer- python
Question: This is the current text that i've but the regex isn't correct to split the
sentences correction. please help to correct my regex, thank you.
import nltk
import os, sys, re, glob
from nltk.tokenize import RegexpTokenizer
jp_sent_tokenizer = nltk.RegexpTokenizer(u'[^ 「」！？。]*[！？。]')
para = []
para.append (jp_sent_tokenizer.tokenize(u' 「オタ」とも呼ばれているこのペラナカン（華人）の特製料理は、とてもおいしいスナック料理です。これは、ココナッツミルクやチリペースト、レモングラス、ガーリックと一緒に魚を砕き、それを、蒸して柔らかくしたバナナの葉に包んで炭火で軽く焼いた料理です。このレシピは、アジアの数地域で知られています。「オタオタ（otak otak ）」は、マレー語で「脳」を意味します。この「オタオタ」という名前は、この料理の柔らかくトロリとした食感から由来しています。魚を使ったオタオタが、最も一般的ですが、エビやイカ、カニ、魚の頭などを用いたものなど、そのバリエーションは豊富です。 ')
for index in range(len(para[0])):
print para[0][index]
print 'this is eos'
#print line
print 'this is eop'
I'm getting this output:
とも呼ばれているこのペラナカン（華人）の特製料理は、とてもおいしいスナック料理です。
this is eos
これは、ココナッツミルクやチリペースト、レモングラス、ガーリックと一緒に魚を砕き、それを、蒸して柔らかくしたバナナの葉に包んで炭火で軽く焼いた料理です。
this is eos
このレシピは、アジアの数地域で知られています。
this is eos
を意味します。
this is eos
という名前は、この料理の柔らかくトロリとした食感から由来しています。
this is eos
魚を使ったオタオタが、最も一般的ですが、エビやイカ、カニ、魚の頭などを用いたものなど、そのバリエーションは豊富です。
this is eos
this is eop
The correct output should be this:
「オタ」とも呼ばれているこのペラナカン（華人）の特製料理は、とてもおいしいスナック料理です。
this is eos
これは、ココナッツミルクやチリペースト、レモングラス、ガーリックと一緒に魚を砕き、それを、蒸して柔らかくしたバナナの葉に包んで炭火で軽く焼いた料理です。
this is eos
このレシピは、アジアの数地域で知られています。
this is eos
「オタオタ（otak otak ）」は、マレー語で「脳」を意味します。
this is eos
「オタオタ（otak otak ）」は、マレー語で「脳」を意味します。この「オタオタ」という名前は、この料理の柔らかくトロリとした食感から由来しています。
this is eos
魚を使ったオタオタが、最も一般的ですが、エビやイカ、カニ、魚の頭などを用いたものなど、そのバリエーションは豊富です。
this is eos
this is eop
Answer: Try this:
u'[^！？。]*[！？。]'
It looks like quotes (「」) do belong in sentences, to you want to allow them.
I should warn that in general (well, in English grammar), it is very difficult
(or even impossible) to parse whole current sentences. (consider `1.2`, `Dr.
Fleishman`, etc.)
|
How to capture a command prompt window close event in python
Question: I want to capture command window close event from Python.
In other words, when the user tries to close the command prompt window, script
should detect it and display a message like `Do you really want to exit -
Yes/No`
Any suggestions about how to implement this? Please help me in doing this.
Answer:
def on_exit(sig, func=None):
print "exit handler"
There should be two way to do that, if you install pywin32 package, you can :
import win32api
win32api.SetConsoleCtrlHandler(func, True)
Or, using python internal "signal" library, if you are using under *nix
system:
import signal
signal.signal(signal.SIGTERM, func)
|
eclipse, pydev, easy_install-ed eggs problem
Question: I have a problem with eclipse and easy_install'ed packages into virtualenv. If
I have
from sqlalchemy.ext.serializer import loads
import statement and put mouse cursor on "load" I get message
loads Found at: __module_not_in_the_pythonpath__
and it repeats with any module on `PYTHONPATH` while I have not manually add
it to the `Project properties -> PyDev - PYTHONPATH -> External Libraries` :/
Like `~/Work/Environments/Default/lib/python2.6/site-
packages/Pylons-1.0-py2.6.egg` or any other egg pkg dir...
`~/Work/Environments/Default/lib/python2.6/site-packages/` is added but
eclipse can't see any eggs inside it!
Python interpreter is set to `~/Work/Environments/Default/bin/python2.6`
I use eclipse-SDK-3.7M5-linux-gtk with latest PyDev.
Can someone help me with that?
Answer: If you add a package after configuring the interpreter in Eclipse, you need to
configure the interpreter again
See [PyDev's manual](http://pydev.org/manual_101_interpreter.html#what-if-i-
add-something-new-in-my-system-pythonpath-after-configuring-it):
> If you add something to your python installation, you need to either add it
> manually as a 'new folder' in the System PYTHONPATH (if it's still not under
> a folder in the PYTHONPATH) or (recommended) remove your interpreter and add
> it again, then, press apply.
Note that adding the libraries in the project settings is not the recommended
approach - it should be used only for some explicit additional library that is
not in the standard PYTHONPATH but is used in a specific application.
|
Using ctypes with jython
Question: I have a trouble with using ctypes lib in my python script. Here is my code
(found on the Internet):
if __name__ == "__main__":
from ctypes import *
user32 = windll.user32
kernel32 = windll.kernel32
class RECT(Structure):
_fields_ = [
("left", c_ulong),
("top", c_ulong),
("right", c_ulong),
("bottom", c_ulong)];
class GUITHREADINFO(Structure):
_fields_ = [
("cbSize", c_ulong),
("flags", c_ulong),
("hwndActive", c_ulong),
("hwndFocus", c_ulong),
("hwndCapture", c_ulong),
("hwndMenuOwner", c_ulong),
("hwndMoveSize", c_ulong),
("hwndCaret", c_ulong),
("rcCaret", RECT)
]
def moveCursorInCurrentWindow(x, y):
# Find the focussed window.
guiThreadInfo = GUITHREADINFO(cbSize=sizeof(GUITHREADINFO))
user32.GetGUIThreadInfo(0, byref(guiThreadInfo))
focussedWindow = guiThreadInfo.hwndFocus
# Find the screen position of the window.
windowRect = RECT()
user32.GetWindowRect(focussedWindow, byref(windowRect))
# Finally, move the cursor relative to the window.
user32.SetCursorPos(windowRect.left + x, windowRect.top + y)
if __name__ == '__main__':
# Quick test.
moveCursorInCurrentWindow(100, 100)
The first problem was that python couldn't find the ctypes so i copied the
files downloaded from the project site to
netbeans\6.9\jython-2.5.1\Lib\
(yep, im using netbeans) and then it shows this error:
> from ctypes import *
> File "C:\Users\k\.netbeans\6.9\jython-2.5.1\Lib\ctypes\__init__.py", line 10, in <module>
> from _ctypes import Union, Structure, Array
Just like the init file has some errors o_O Help guys! Greetings, Chris
Answer: `ctypes` in Jython experimental and not complete.
From the jython-users mailing list in a thread titled "[ctypes in
Jython](http://sourceforge.net/mailarchive/forum.php?thread_name=AANLkTikZpn1%2Bkbjd-0z1-sBd%2BGf7BQSLCcD7tj%2B%2BTC3k%40mail.gmail.com&forum_name=jython-
users)" Jim Baker (a Jython committer) wrote on November 17, 2010:
> There's some experimental support for ctypes in 2.5.2 [the current version],
> but it's really more of a placeholder at this point.
He then suggests these work arounds:
> I do recommend JNA if you can modify your ctypes code. JNA is pretty close
> to ctypes - JNA's API apparently was significantly influenced by ctypes! JNA
> also seems to work well with Jython.
>
> The other option is to use something like execnet. For execnet specifically:
> it allows you to pair Jython with CPython, and it does seem to work well.
> But its GPL license makes it a non starter for many people. There are other
> choices out there too.
Further on in the same thread we have this confirming assessment:
> I tried the ctypes module in 2.5.2rc2 recently, and found that: 1) There's
> no ctypes.util.find_library yet 2) ctypes.Structure doesn't support non-
> scalar types yet
>
> So I agree with the "more of a placeholder" assessment. Still, it's exciting
> to see it getting started.
|
Django manage.py shell Throws error when meet "def"
Question: I am reading django official tutorial (
<http://docs.djangoproject.com/en/dev/intro/tutorial01/> ). When i try run
"python manage.py shell", python throw error:
File "D:\DjangoProjects\mysite\polls\models.py", line 8
def __unicode__(self):
^
IndentationError: unexpected indent
Help please! How solve this problem?
models.py:
import datetime
from django.db import models
# Create your models here.
class Poll(models.Model):
question = models.CharField(max_length=200)
pub_date = models.DateTimeField('date published')
def __unicode__(self):
return self.question
class Choice(models.Model):
poll = models.ForeignKey(Poll)
choice = models.CharField(max_length=200)
votes = models.IntegerField()
def __unicode__(self):
return self.choice
Answer: You have a python indentation error. I'm not exactly sure where, but the
django docs show this:
<http://docs.djangoproject.com/en/dev/intro/tutorial01/>
So follow it to the letter /space.
class Poll(models.Model):
# ...
def __unicode__(self):
return self.question
Your exact indentation you've pasted wouldn't throw that error, but in your
real code, you must have the `def __unicode__` line at the exact indent depth
as the other lines in your model.
Make sure you are using spaces and not tabs for all of your indents, as tabs
can sometimes make the indent level seem the same as the others.
|
Call subprocess.Popen() when the working directory is on a UNC path, not a mapped drive
Question: I would like to run an executable that performs some processing on a dataset
located on a remote filer. As part of the design, I'd like the location of the
filer to be flexible and something that's passed to my python program at
runtime.
I've put together the following bit of code that illustrates my problem, but
using the `python` command, so anyone can run this:
#!/usr/bin/env python
import os
import subprocess
def runMySubProcess(cmdstr, iwd):
p = subprocess.Popen(cmdstr,
shell=True,
cwd=iwd,
stdout=subprocess.PIPE,
stderr=subprocess.PIPE)
(stdout, stderr) = p.communicate()
if stderr:
raise IOError, stderr
return stdout
if __name__ == '__main__':
print runMySubProcess('python -h', 'C:\\')
print runMySubProcess('python -h', '\\\\htpc\\nas')
This works great as long as `iwd` is on a share that's be mapped to a drive
letter on the machine. But if `iwd` is a UNC path the `subprocess.Popen()`
call ends up with stderr output, which in turn throws the IOError exception:
Traceback (most recent call last):
File "test.py", line 19, in <module>
print runMySubProcess('dir', '\\\\htpc\\nas')
File "test.py", line 14, in runMySubProcess
raise IOError, stderr
IOError: '\\htpc\nas'
CMD.EXE was started with the above path as the current directory.
UNC paths are not supported. Defaulting to Windows directory.
Is there a way to make this subprocess call work _without_ resorting to
parsing `iwd` and making a temporary drive mount on the machine that exists
while the subprocess command executes? I want to avoid having to manage the
creation and cleanup of drive mounts. And of course, I'd rather not have to
deal with (albeit unlikely) case where all drive letters are currently in use
on the machine.
Answer: The problem is not with `Popen,`, but with `cmd.exe`, which does not allow the
working directory to be a UNC path. It just does not; try it. You may have
better luck specifying `shell=False` on your `Popen()` call, assuming that
whatever executable you're running can handle a UNC path, but of course if
what you're trying to run is a command that's built in to `cmd.exe` you don't
have a choice.
|
Can't set the shop language in Satchmo
Question: I'm trying to set the default and only shop language of a Satchmo 0.9.2
installationto Dutch.
I'm following the instructions on [translating
content](http://www.satchmoproject.com/docs/dev/translation.html):
From the directory
`/home/myusername/webapps/myshop/lib/python2.7/Satchmo-0.9.2-py2.7.egg` I
issued the following command to compile the Dutch langauge files:
find . -name locale -exec sh -c 'cd $0 && cd ../ && python2.7
/home/myusername/webapps/myshop/lib/python2.7/django/bin/django-admin.py
makemessages -l nl -e html,txt,rml' {} \;
I can now see multiple `.../locale/nl/LC_MESSAGES/django.po` files wich
contain messagestrings translated into Dutch.
My `local_settings.py` file has a `LOCALE_PATHS` variable defined:
LOCALE_PATHS = ""
I have compiled the `.po` files to `.mo` files with:
find . -name locale -exec sh -c 'cd $0 && cd ../ && python2.7
/home/myusername/webapps/myshop/lib/python2.7/django/bin/django-admin.py
compilemessages' {} \;
I only want text to appear in Dutch, so my `local_settings.py` only contains:
LANGUAGE_CODE = 'nl'
LANGUAGES = (
('nl', "Nederlands"),
)
Users should not be ablo to choose other translations, so
`allow_translation_choice` is set to `False` in `settings.py`:
L10N_SETTINGS = {
'currency_formats' : {
'EURO' : {'symbol': u'€', 'positive' : u"€%(val)0.2f", 'negative':
u"€(%(val)0.2f)",
'decimal' : ','},
},
'default_currency' : 'EURO',
'show_admin_translations': True,
'allow_translation_choice': False,
}
and in the same file I have enabled my i18n urls:
SATCHMO_SETTINGS = {
'SHOP_BASE' : '',
'MULTISHOP' : False,
'SHOP_URLS' : patterns('', (r'^i18n/', include('l10n.urls')),)
}
To make sure that my templates use the correct language code, I also have in
`settings.py`:
TEMPLATE_CONTEXT_PROCESSORS = (
'satchmo_store.shop.context_processors.settings',
'django.core.context_processors.auth',
'django.core.context_processors.i18n',
)
After jumping through all these hoops, my shop language still shows up in
English and still has the 'Change language' with an empty drop-down button in
the lower right corner.
Anyone have a clue where I went wrong?
Thanks in advance.
Answer: The only necessary steps to enable switching languages are:
1) Change languages in local_settings.py:
LANGUAGE_CODE = 'nl' # not as important as would expected
LANGUAGES = (
('nl', "Nederlands"), # languages supported by you
)
2) Enable switching by adding the following line to the dictionary
SATCHMO_SETTINGS in settings.py:
'SHOP_URLS' : patterns('', (r'^i18n/', include('l10n.urls')),),
Select your language on the web page.
Notes:
I have verified now the previous with new installed old Satchmo valid at the
date of your report. (last change at end of Februar 2011)
For sure look that no previous value is set later to a different value in
settings.py or local_settings.py.
I am not sure that LANGUAGE_CODE does what is expected by most people. It is
used only if user did not selected any language manually and the language
preferred by user's browser is not enabled by site. Therefore I usually
disable English.
If you are adding a new language to Satchmo, verify that it is in
`django/conf/locale`. (there are more than 50 languages) Otherwise use
FORMAT_MODULE_PATH and read Django documentation about it.
|
Why are my pygame images not loading?
Question: I found a tutorial online (on Youtube) and it showed me the basics of creating
a game with pygame. i found images of the kind he said and what he had. he
didn't say where to save them to, i think that may be my problem. here, this
is an example of what i have in my program and what shows up on the error
bif="bg.jpg"
mif="images.png"
import pygame, sys
from pygame.locals import *
pygame.init()
screen=pygame.display.set_mode((420,315),0,32)
backround=pygame.image.load(bif).convert()
mouse_c=pygame.image.load(mif).convert_alpha()
while True:
for event in pygame.event.get():
if event.type == QUIT:
pygame.quit()
sys.exit()
screen.blit(backround, (0,0))
x,y = pygame.mouse.get_pos()
x -= mouse_c.get_width()/2
y -+ mouse_c.get_height()/2
screen.blit(mouse_c, (x,y))
pygame.display.update()
the error reads:
Traceback (most recent call last):
File "C:/Python26/pygame.games/pygame
1", line 10, in <module>
backround=pygame.image.load(bif).convert()
error: Couldn't open bg.jpg
please respond as soon as possible.
Answer: Based on that code, your image files need to be saved in the same directory as
your game's .py file. Try moving them there.
As a sanity check (to make sure the images will load and it is in fact an
issue with supplying the correct path) you could temporarily specify an
absolute path to the image in your code, so instead of
bif = "bg.jpg"
You would have
bif = "C:/My_game/images/bg.jpg"
But obviously change the second bit to point to where your image is actually
stored. Once you're sure that the image can be loaded using an absolute path,
you should use a relative path, and if you're likely to have many assets you
should keep them separate from the code, for example by putting them in an
`assets` folder in the same folder as your game code, or similar.
bif = "assets/bg.jpg"
|
IronPython: Cannot import 'Rect'-struct from System.Windows
Question: When I try to import the 'Rect'-struct from System.Windows, IronPython-
Interpreter claims that it cannot import.
Since I am using the IronPython Tools for Visual Studio, i can also see that
the IntelliSense-DropDown does not show this struct.
Is there a need for a special statement for importing this struct?
Thanks!
Answer: You probably need to do:
import clr clr.AddReference('WindowsBase')
to load the assembly Rect is declared in before importing it.
|
Python v3 Logging
Question: I could use this code below on Python 2. I tried it on Python 3 and I got an
error. Anyone could explain why?
Code:
import logging
import logging.handlers
LOG_FILENAME = 'poller.log'
# Set up a specific logger with our desired output level
poll_logger = logging.getLogger('pollerLog')
# Add the log message handler to the logger
log_rotator = logging.handlers.TimedRotatingFileHandler(LOG_FILENAME, when='d', interval=1, backupCount=5, encoding=None, delay=False, utc=False)
poll_logger.addHandler(log_rotator)
# Roll over on application start
poll_logger.handlers[0].doRollover()
Error:
Traceback (most recent call last):
File "logR.py", line 10, in <module>
log_rotator = logging.handlers.TimedRotatingFileHandler(LOG_FILENAME, when='d', interval=1, back
upCount=5, encoding=None, delay=False, utc=False)
File "C:\LynxApps\Python31\lib\logging\handlers.py", line 206, in __init__
t = os.stat(filename)[ST_MTIME]
NameError: global name 'ST_MTIME' is not defined
I checked out the documents below and I don't see any difference:
Python v2 -->
<http://docs.python.org/library/logging.html#timedrotatingfilehandler>
Python v3 -->
<http://docs.python.org/py3k/library/logging.handlers.html?highlight=logging#timedrotatingfilehandler>
Answer: It's a bug in Python 3.1.3 (see the [issue on
bugs.python.org](http://bugs.python.org/issue10810)).
Supposedly it's fixed in Python 3.2.
|
Best way to log a Python exception
Question: I'm printing my exceptions to a log file currently with:
try:
# coode in here
except Exception, e:
logging.error(e)
Could I be printing more information about the exception and the code that
generated it than just the exception string? Things like line numbers or stack
traces would be great.
Answer: [`logger.exception`](http://docs.python.org/library/logging.html#logging.Logger.exception)
does that.
For example:
import logging
try:
1/0
except Exception as e:
logging.exception("message")
Output:
ERROR:root:message
Traceback (most recent call last):
File "<stdin>", line 2, in <module>
ZeroDivisionError: integer division or modulo by zero
[@Paulo Cheque](http://stackoverflow.com/users/1163081/paulo-cheque) notes,
"be aware that in Python 3 you must call the `logging.exception` method just
inside the `except` part. If you call this method in an arbitrary place you
may get a bizarre exception. The docs alert about that."
|
Broadcasting a python function on to numpy arrays
Question: Let's say we have a particularly simple function like
import scipy as sp
def func(x, y):
return x + y
This function evidently works for several builtin python datatypes of `x` and
`y` like string, list, int, float, array, etc. Since we are particularly
interested in arrays, we consider two arrays:
x = sp.array([-2, -1, 0, 1, 2])
y = sp.array([-2, -1, 0, 1, 2])
xx = x[:, sp.newaxis]
yy = y[sp.newaxis, :]
>>> func(xx, yy)
this returns
array([[-4, -3, -2, -1, 0],
[-3, -2, -1, 0, 1],
[-2, -1, 0, 1, 2],
[-1, 0, 1, 2, 3],
[ 0, 1, 2, 3, 4]])
just as we would expect.
Now what if one wants to throw in arrays as the inputs for the following
function?
def func2(x, y):
if x > y:
return x + y
else:
return x - y
doing `>>>func(xx, yy)` would raise an error.
The first obvious method that one would come up with is the `sp.vectorize`
function in scipy/numpy. This method, nevertheless has been proved to be not
very efficient. Can anyone think of a more robust way of broadcasting any
function in general on to numpy arrays?
If re-writing the code in an array-friendly fashion is the only way, it would
help if you could mention it here too.
Answer: `np.vectorize` is a general way to convert Python functions that operate on
numbers into numpy functions that operate on ndarrays.
However, as you point out, it isn't very fast, since it is using a Python loop
"under the hood".
To achieve better speed, you have to hand-craft a function that expects numpy
arrays as input and takes advantage of that numpy-ness:
import numpy as np
def func2(x, y):
return np.where(x>y,x+y,x-y)
x = np.array([-2, -1, 0, 1, 2])
y = np.array([-2, -1, 0, 1, 2])
xx = x[:, np.newaxis]
yy = y[np.newaxis, :]
print(func2(xx, yy))
# [[ 0 -1 -2 -3 -4]
# [-3 0 -1 -2 -3]
# [-2 -1 0 -1 -2]
# [-1 0 1 0 -1]
# [ 0 1 2 3 0]]
* * *
Regarding performance:
**test.py** :
import numpy as np
def func2a(x, y):
return np.where(x>y,x+y,x-y)
def func2b(x, y):
ind=x>y
z=np.empty(ind.shape,dtype=x.dtype)
z[ind]=(x+y)[ind]
z[~ind]=(x-y)[~ind]
return z
def func2c(x, y):
# x, y= x[:, None], y[None, :]
A, L= x+ y, x<= y
A[L]= (x- y)[L]
return A
N=40
x = np.random.random(N)
y = np.random.random(N)
xx = x[:, np.newaxis]
yy = y[np.newaxis, :]
Running:
With N=30:
% python -mtimeit -s'import test' 'test.func2a(test.xx,test.yy)'
1000 loops, best of 3: 219 usec per loop
% python -mtimeit -s'import test' 'test.func2b(test.xx,test.yy)'
1000 loops, best of 3: 488 usec per loop
% python -mtimeit -s'import test' 'test.func2c(test.xx,test.yy)'
1000 loops, best of 3: 248 usec per loop
With N=1000:
% python -mtimeit -s'import test' 'test.func2a(test.xx,test.yy)'
10 loops, best of 3: 93.7 msec per loop
% python -mtimeit -s'import test' 'test.func2b(test.xx,test.yy)'
10 loops, best of 3: 367 msec per loop
% python -mtimeit -s'import test' 'test.func2c(test.xx,test.yy)'
10 loops, best of 3: 186 msec per loop
This seems to suggest that `func2a` is slightly faster than `func2c` (and
`func2b` is horribly slow).
|
Improving Postgres psycopg2 query performance for Python to the same level of Java's JDBC driver
Question: # Overview
I'm attempting to improve the performance of our database queries for
SQLAlchemy. We're using psycopg2. In our production system, we're chosing to
go with Java because it is simply faster by at least 50%, if not closer to
100%. So I am hoping someone in the Stack Overflow community has a way to
improve my performance.
I think my next step is going to be to end up patching the psycopg2 library to
behave like the JDBC driver. If that's the case and someone has already done
this, that would be fine, but I am hoping I've still got a settings or
refactoring tweak I can do from Python.
# Details
I have a simple "SELECT * FROM someLargeDataSetTable" query running. The
dataset is GBs in size. A quick performance chart is as follows:
## Timing Table
Records | JDBC | SQLAlchemy[1] | SQLAlchemy[2] | Psql
--------------------------------------------------------------------
1 (4kB) | 200ms | 300ms | 250ms | 10ms
10 (8kB) | 200ms | 300ms | 250ms | 10ms
100 (88kB) | 200ms | 300ms | 250ms | 10ms
1,000 (600kB) | 300ms | 300ms | 370ms | 100ms
10,000 (6MB) | 800ms | 830ms | 730ms | 850ms
100,000 (50MB) | 4s | 5s | 4.6s | 8s
1,000,000 (510MB) | 30s | 50s | 50s | 1m32s
10,000,000 (5.1GB) | 4m44s | 7m55s | 6m39s | n/a
--------------------------------------------------------------------
5,000,000 (2.6GB) | 2m30s | 4m45s | 3m52s | 14m22s
--------------------------------------------------------------------
[1] - With the processrow function
[2] - Without the processrow function (direct dump)
I could add more (our data can be as much as terabytes), but I think changing
slope is evident from the data. JDBC just performs significantly better as the
dataset size increases. Some notes...
## Timing Table Notes:
* The datasizes are approximate, but they should give you an idea of the amount of data.
* I'm using the 'time' tool from a Linux bash commandline.
* The times are the wall clock times (i.e. real).
* I'm using Python 2.6.6 and I'm running with `python -u`
* Fetch Size is 10,000
* I'm not really worried about the Psql timing, it's there just as a reference point. I may not have properly set fetchsize for it.
* I'm also really not worried about the timing below the fetch size as less than 5 seconds is negligible to my application.
* Java and Psql appear to take about 1GB of memory resources; Python is more like 100MB (yay!!).
* I'm using the [[cdecimals]](http://www.bytereef.org/mpdecimal/doc/cdecimal/index.html) library.
* I noticed a [[recent article]](http://osdir.com/ml/pgsql-performance/2010-12/msg00197.html) discussing something similar to this. It appears that the JDBC driver design is totally different to the psycopg2 design (which I think is rather annoying given the performance difference).
* My use-case is basically that I have to run a daily process (with approximately 20,000 different steps... multiple queries) over very large datasets and I have a very specific window of time where I may finish this process. The Java we use is not simply JDBC, it's a "smart" wrapper on top of the JDBC engine... we don't want to use Java and we'd like to stop using the "smart" part of it.
* I'm using one of our production system's boxes (database and backend process) to run the query. So this is our best-case timing. We have QA and Dev boxes that run much slower and the extra query time can become significant.
## testSqlAlchemy.py
#!/usr/bin/env python
# testSqlAlchemy.py
import sys
try:
import cdecimal
sys.modules["decimal"]=cdecimal
except ImportError,e:
print >> sys.stderr, "Error: cdecimal didn't load properly."
raise SystemExit
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
def processrow (row,delimiter="|",null="\N"):
newrow = []
for x in row:
if x is None:
x = null
newrow.append(str(x))
return delimiter.join(newrow)
fetchsize = 10000
connectionString = "postgresql+psycopg2://usr:pass@server:port/db"
eng = create_engine(connectionString, server_side_cursors=True)
session = sessionmaker(bind=eng)()
with open("test.sql","r") as queryFD:
with open("/dev/null","w") as nullDev:
query = session.execute(queryFD.read())
cur = query.cursor
while cur.statusmessage not in ['FETCH 0','CLOSE CURSOR']:
for row in query.fetchmany(fetchsize):
print >> nullDev, processrow(row)
After timing, I also ran a cProfile and this is the dump of worst offenders:
## Timing Profile (with processrow)
Fri Mar 4 13:49:45 2011 sqlAlchemy.prof
415757706 function calls (415756424 primitive calls) in 563.923 CPU seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.001 0.001 563.924 563.924 {execfile}
1 25.151 25.151 563.924 563.924 testSqlAlchemy.py:2()
1001 0.050 0.000 329.285 0.329 base.py:2679(fetchmany)
1001 5.503 0.005 314.665 0.314 base.py:2804(_fetchmany_impl)
10000003 4.328 0.000 307.843 0.000 base.py:2795(_fetchone_impl)
10011 0.309 0.000 302.743 0.030 base.py:2790(__buffer_rows)
10011 233.620 0.023 302.425 0.030 {method 'fetchmany' of 'psycopg2._psycopg.cursor' objects}
10000000 145.459 0.000 209.147 0.000 testSqlAlchemy.py:13(processrow)
## Timing Profile (without processrow)
Fri Mar 4 14:03:06 2011 sqlAlchemy.prof
305460312 function calls (305459030 primitive calls) in 536.368 CPU seconds
Ordered by: cumulative time
ncalls tottime percall cumtime percall filename:lineno(function)
1 0.001 0.001 536.370 536.370 {execfile}
1 29.503 29.503 536.369 536.369 testSqlAlchemy.py:2()
1001 0.066 0.000 333.806 0.333 base.py:2679(fetchmany)
1001 5.444 0.005 318.462 0.318 base.py:2804(_fetchmany_impl)
10000003 4.389 0.000 311.647 0.000 base.py:2795(_fetchone_impl)
10011 0.339 0.000 306.452 0.031 base.py:2790(__buffer_rows)
10011 235.664 0.024 306.102 0.031 {method 'fetchmany' of 'psycopg2._psycopg.cursor' objects}
10000000 32.904 0.000 172.802 0.000 base.py:2246(__repr__)
# Final Comments
Unfortunately, the processrow function needs to stay unless there is a way
within SQLAlchemy to specify null = 'userDefinedValueOrString' and delimiter =
'userDefinedValueOrString' of the output. The Java we are using currently
already does this, so the comparison (with processrow) needed to be apples to
apples. If there is a way to improve the performance of either processrow or
SQLAlchemy with pure Python or a settings tweak, I'm very interested.
Answer: The stuff below is probably aiming above and beyond what you have in mind or
what is deemed acceptable in your environment, but I'll put the option on the
table just in case.
1. Is the destination of every `SELECT` in your `test.sql` truly a simple `|`-separated results file?
2. Is non-portability (Postgres-specificity) acceptable?
3. Is your backend Postgres 8.2 or newer?
4. Will the script run on the same host as the database backend, or would it be acceptable to generate the `|`-separated results file(s) from within the backend (e.g. to a share?)
If the answer to all of the above questions is _yes_ , then you can transform
your `SELECT ...` statements to `COPY ( SELECT ... ) TO E'path-to-results-
file' WITH DELIMITER '|' NULL E'\\N'`.
|
Why bother to limit the types imported from a python package?
Question: When using many IDEs that support autocompletion with Python, things like this
will show warnings, which I find annoying:
from eventlet.green.httplib import BadStatusLine
When switching to:
from eventlet.green.httplib import *
The warnings go away. What's the benefit to limiting imports to a specific set
of types you'll use? Is the parsing faster? Reduces collisions? What other
point is there? It seems the state of python IDEs and the nature of the typing
system makes it hard for many IDEs to fully get right when a type import works
and when it doesn't.
Answer: By typing `from foo import *`, you import _all_ the names defined in `foo`
into the global namespace. This is bad practice because you could have name
clashes both with other modules and with built-ins.
For example, consider a module `foo`
#foo.py
def open(something):
pass
and a module `bar`:
#bar.py
def open(something_else):
pass
Now, `from foo import *` hides the built-in function `open()` which means that
any calls to `open()` now refer to `foo.open()` rather than the built-in.
Worse, if you then have `from bar import *`, the function `open()` in `bar`
now hides both the built-in _and_ the function imported from `foo`.
In the example above, `from foo import open` is equally shadowing the built-in
function, but one glance at the code tells you why you can't open files for IO
anymore.
This is why you should import only specific names, ensuring that you _know_
what names are imported. Alternatively, you could use fully qualified names
(`import foo; foo.open()`, which is perfectly safe).
EDIT: Just as a note, this can be horribly compounded if the module you're
importing also uses `from x import *`. In this case, not only do you typically
import all the stuff in the module `foo`, but also all the stuff in the module
`x` into the global namespace. This can very quickly turn into an absolute
mess.
|
Python cpu temp in system tray Linux
Question: I'm using tint2 for a panel and want to show the cpu temp as a system tray
icon since there aren't any plugins for tint2 that do that and I'd just like
to know how to do this anyway whether there was one or not. The script I have
so far is:
#! /usr/bin/python
import pygtk,os
pygtk.require("2.0")
import gtk
import egg.trayicon
t = egg.trayicon.TrayIcon("CPUTemp")
cpu_temp=os.popen('sensors | grep "temp1:" | cut -d+ -f2 | cut -c1-2').read()
t.add(gtk.Label(cpu_temp))
t.show_all()
gtk.main()
Basically, it works the first time around but I'd also like it to update every
5 seconds or so. Any help greatly appreciated.
Answer: you can define a timer via
[timeout_add_seconds](http://library.gnome.org/devel/pygobject/stable/glib-
functions.html#function-glib--timeout-add-seconds) and update your tray icon
in the callback. See if an example below would work for you:
import gtk, gobject, os
class CPUTimer:
def __init__(self, timeout):
self.window = gtk.Window()
vbox = gtk.VBox()
self.window.add(vbox)
self.label = gtk.Label('CPU')
self.label.set_size_request(200, 40)
vbox.pack_start(self.label)
# register a timer
gobject.timeout_add_seconds(timeout, self.timer_callback)
self.window.connect("destroy", lambda w: gtk.main_quit())
self.window.connect("delete_event", lambda w, e: gtk.main_quit())
self.window.show_all()
self.timer_callback()
def timer_callback(self):
cpu_temp = os.popen('sensors | grep "temp1:" | cut -d+ -f2 | cut -c1-2').read()
print 'update CPU: ' + cpu_temp
self.label.set_text('CPU: ' + cpu_temp)
return True
if __name__ == '__main__':
timer = CPUTimer(1) # sets 1 second update interval
gtk.main()
hope this helps, regards
|
non-prime factorings with some repeats
Question: Let's say we have numbers factors, for example 1260:
>>> factors(1260)
[2, 2, 3, 3, 5, 7]
Which would be best way to do in Python combinations with every subproduct
possible from these numbers, ie all factorings, not only prime factoring, with
**sum of factors** less than **max_product**?
If I do combinations from the prime factors, I have to refactor remaining part
of the product as I do not know the remaining part not in combination.
I can also refine my **divisors** function to produce pairs of divisors
instead of divisors in size order, but still it will cost me to do this for
number with **product upto 12000**. The product must remain always the same.
I was linked to divisor routine, but it did not look worth the effort to prove
them to adopt to my other code. At least my divisor function is noticably
faster than sympy one:
def divides(number):
if number<2:
yield number
return
high = [number]
sqr = int(number ** 0.5)
limit = sqr+(sqr*sqr != number)
yield 1
for divisor in xrange(3, limit, 2) if (number & 1) else xrange(2, limit):
if not number % divisor:
yield divisor
high.append(number//divisor)
if sqr*sqr== number: yield sqr
for divisor in reversed(high):
yield divisor
Only problem to reuse this code is to link the divisors to factoring sieve or
do some kind of itertools.product of divisors of the divisors in pairs, which
I would give out as pairs instead of sorting to order.
Example results would be:
[4, 3, 3, 5, 7] (one replacement of two)
[5, 7, 36] (one replacement of three)
[3, 6, 14, 5] (two replacements)
Probably I would need some way to produce sieve or dynamic programming
solutions for smaller divisors which could be linked to numbers whose divisors
they are. Looks difficult to avoid overlap though. I do have one sieve
function ready which stores biggest prime factor for each number for speeding
up the factoring without saving complete factorings of every number... maybe
it could be adapted.
**UPDATE: The sum of factors should be near the product, so probably there is
high number of factors of <= 10 in answer (upto 14 factors).**
**UPDATE2:** Here is my code, but must figure out how to do multiple removals
recursively or iteratively for parts > 2 long and dig up the lexical
partitioning to replace the jumping bit patterns which produce duplicates
(pathetic hit count only for one replacement, and that does not count the
passing of 'single element partionings' inside the single_partition):
from __future__ import print_function
import itertools
import operator
from euler import factors
def subset(seq, mask):
""" binary mask of len(seq) bits, return generator for the sequence """
# this is not lexical order, replace with lexical order masked passing duplicates
return (c for ind,c in enumerate(seq) if mask & (1<<ind))
def single_partition(seq, n = 0, func = lambda x: x):
''' map given function to one partition '''
for n in range(n, (2**len(seq))):
result = tuple(subset(seq,n))
others = tuple(subset(seq,~n))
if len(result) < 2 or len(others) == 0:
#empty subset or only one or all
continue
result = (func(result),)+others
yield result
if __name__=='__main__':
seen, hits, count = set(), 0, 0
for f in single_partition(factors(13824), func = lambda x: reduce(operator.mul, x)):
if f not in seen:
print(f,end=' ')
seen.add(f)
else:
hits += 1
count += 1
print('\nGenerated %i, hits %i' %(count,hits))
**REFINEMENT** I am happy to get only the factorings with max 5 factors in the
non-prime factor parts. I have found by hand that non-decreasing arrangements
for up to 5 same factors follow this form:
partitions of 5 applied to 2**5
1 1 1 1 1 2 2 2 2 2
1 1 1 2 2 2 2 4
1 1 1 3 2 2 8
1 2 2 2 4 4
1 4 2 16
2 3 4 8
**THE SOLUTION** I do not remove the accepted answer from fine solution down,
but it is over complicated for the job. From Project Euler I reveal only this
helper function from orbifold of NZ, it works faster and without needing the
prime factors first:
def factorings(n,k=2):
result = []
while k*k <= n:
if n%k == 0:
result.extend([[k]+f for f in factorings(n/k,k)])
k += 1
return result + [[n]]
The relevant **solution for problem 88** of his run in Python 2.7 in 4.85 s by
my timing decorator and after optimizing the stop condition by found counter
**3.4 s in 2.6.6 with psyco** , 3.7 s in 2.7 without psyco . Speed of **my own
code** went from 30 seconds with code in accepted answer (sorting added by me
removed) to 2.25 s (2.7 without psyco) and **782 ms with psyco in Python
2.6.6.**
Answer: What you are looking for is more commonly called a **divisor**. This answers
to [this question](http://stackoverflow.com/questions/171765/what-is-the-best-
way-to-get-all-the-divisors-of-a-number) may help you.
|
Python C-API and Numpy: core dump on import_array
Question:
//testNumpy.c
#include<Python.h>
#include<numpy/arrayobject.h>
#include<stdio.h>
int main(){
printf("import_array\n");fflush(stdout);
import_array();
printf("import_array done\n");fflush(stdout);
}
$ gcc -I/usr/include/python2.6 -lpython2.6 testNumpy.c&&./a.out
import_array
Segmentation fault (core dumped)
What could I possibly be doing wrong on such a simple program? I'm tearing my
hair out :-)
Answer: For starters, you did not initialize Python properly. Call
[Py_Initialize()](http://docs.python.org/c-api/init.html) before trying to
initialize NumPy.
|
Sorting a Python list by two criteria
Question: I have the following list created from a sorted csv
list1 = sorted(csv1, key=operator.itemgetter(1))
I would actually like to sort the list by two criteria: first by the value in
field 1 and then by the value in field 2. How do I do this?
Answer: Replying to this dead thread for archive.
No need to import anything when using lambda functions.
The following sorts `list` by the first element, then by the second element.
sorted(list, key=lambda x: (x[0], -x[1]))
|
Python - slice array until certain condition is met
Question: I need to slice an array from a given index until a certain condition is met.
>>> a = numpy.zeros((10), dtype='|S1')
>>> a[2] = 'A'
>>> a[4] = 'X'
>>> a[8] = 'B'
>>> a
array(['', '', 'A', '', 'X', '', '', '', 'B', ''], dtype='|S1')
For instance, for the above array I want a subset from a given index until
first non-zero values in both directions. For example, for index values 2, 4,
8 the results would be:
['', '', A, ''] # 2
['', X, '', '', ''] # 4
['', '', '', B, ''] # 8
Any suggestions on the simplest way to do this using the numpy API? Learning
python and numpy, would appreciate any help. Thanks!
Answer: If you set up your problem like this:
import numpy
a = numpy.zeros((10), dtype=str)
a[2] = 'A'
a[4] = 'X'
a[8] = 'B'
You can easily get the indices of non-empty strings like so:
i = numpy.where(a!='')[0] # array([2, 4, 8])
Alternatively, `numpy.argwhere(..)` also works well.
Then you can slice away using this array:
out2 = a[:i[1]] # 2 ['' '' 'A' '']
out4 = a[i[0]+1:i[2]] # 4 ['' 'X' '' '' '']
etc.
|
How do I perform binary search on a text file to search a keyword in python?
Question: The text file contains two columns- index number(5 spaces) and characters(30
spaces). It is arranged in lexicographic order. I want to perform binary
search to search for the keyword.
Answer: Here's an interesting way to do it with Python's built-in bisect module.
import bisect
import os
class Query(object):
def __init__(self, query, index=5):
self.query = query
self.index = index
def __lt__(self, comparable):
return self.query < comparable[self.index:]
class FileSearcher(object):
def __init__(self, file_pointer, record_size=35):
self.file_pointer = file_pointer
self.file_pointer.seek(0, os.SEEK_END)
self.record_size = record_size + len(os.linesep)
self.num_bytes = self.file_pointer.tell()
self.file_size = (self.num_bytes // self.record_size)
def __len__(self):
return self.file_size
def __getitem__(self, item):
self.file_pointer.seek(item * self.record_size)
return self.file_pointer.read(self.record_size)
if __name__ == '__main__':
with open('data.dat') as file_to_search:
query = raw_input('Query: ')
wrapped_query = Query(query)
searchable_file = FileSearcher(file_to_search)
print "Located @ line: ", bisect.bisect(searchable_file, wrapped_query)
|
Find and append each reference to a html link - Python
Question: I have a HTML file I got from Wikipedia and would like to find every link on
the page such as `/wiki/Absinthe` and replace it with the current directory
added to the front such as `/home/fergus/wikiget/wiki/Absinthe` so for:
<a href="/wiki/Absinthe">Absinthe</a>
becomes:
<a href="/home/fergus/wikiget/wiki/Absinthe">Absinthe</a>
and this is throughout the whole document.
Do you have any ideas? I'm happy to use BeautifulSoup or Regex!
Answer: If that's really all you have to do, you could do it with `sed` and its `-i`
option to rewrite the file in-place:
sed -e 's,href="/wiki,href="/home/fergus/wikiget/wiki,' wiki-file.html
However, here's a Python solution using the lovely [lxml](http://lxml.de/)
API, in case you need to do anything more complex or you might have badly
formed HTML, etc.:
from lxml import etree
import re
parser = etree.HTMLParser()
with open("wiki-file.html") as fp:
tree = etree.parse(fp, parser)
for e in tree.xpath("//a[@href]"):
link = e.attrib['href']
if re.search('^/wiki',link):
e.attrib['href'] = '/home/fergus/wikiget'+link
# Or you can just specify the same filename to overwrite it:
with open("wiki-file-rewritten.html","w") as fp:
fp.write(etree.tostring(tree))
Note that `lxml` is probably a better option than BeautifulSoup for this kind
of task nowadays, for the
[reasons](http://www.crummy.com/software/BeautifulSoup/3.1-problems.html)
given by BeautifulSoup's author.
|
How Can I Allow Object Editing in the Django Admin For Specific Objects ONLY?
Question: I'm currently writing a site which uses [django-
guardian](http://packages.python.org/django-guardian/index.html) to assign
object-level permissions which are used throughout the site.
**Here is the desired functionality:**
I'd like for a user to have permissions to edit a single object (or multiple
objects). For example, if there is a user named "Joe", and a model named
"Partyline", I may give "Joe" specific permissions to "change_partyline" for 3
specific "Partyline" objects.
When Joe logs into the Django admin panel, I'd like him to be able to edit
ONLY his 3 specific "Partyline" objects, since those are the only things he
has permission to edit.
**Here is the current functionality:**
I can assign Joe change_partyline permissions to 3 Partyline objects--no
problem. And Joe can log into the admin panel just fine. The problem is that
since Joe doesn't have "global" permissions to change ALL partylines, the
admin panel says that he does not have any permissions, and won't let him edit
anything. I'd like to find a way for the admin to recognize that Joe has
permissions to edit only 3 specific objects, and let him view and edit only
those objects which he has permissions to work on.
I'd LOVE to find a way to make this work. I'm using the admin extensively for
my users to manage things right now, and it would really break presentation to
have to move certain functionality out of the admin to other areas on the
site.
If you have any suggestions, please let me know!
For reference, here is some shell output demonstrating that the user has
change_partyline permissions on a Partyline object:
>>> from django.contrib.auth.models import User
>>> u = User.objects.get(id=2)
>>> from apps.partylines.models import Partyline
>>> p = Partyline.objects.get(id=3)
>>> u.has_perm('partylines.change_partyline', p)
True
And here's my `partylines.admin` module (which shows how the Partyline module
is populated in the admin):
from django.contrib import admin
from guardian.admin import GuardedModelAdmin
from apps.partylines.models import Partyline
class PartylineAdmin(GuardedModelAdmin):
list_display = ('did', 'name', 'listed')
ordering = ('did',)
search_fields = ('did', 'name')
admin.site.register(Partyline, PartylineAdmin)
Answer: I've asked a similar question to Lukazs (guardian's author) and he told me
that this feature is coming on a future release (see
user_can_access_owned_objects_only property on [this
commit](https://github.com/lukaszb/django-
guardian/commit/4c7960543f0393a555a841dd89513dbc635bdf45) and the [related
issue](https://github.com/lukaszb/django-guardian/issues/36)). If you're not
willing to wait, maybe you can just install the source on the master branch.
Have you thought about overriding queryset on your model? In my case was just
enough:
# models.py
from django.db import models
from django.contrib.auth import models as auth_models
class MagazineUser(models.Model):
user = models.ForeignKey(auth_models.User, unique=True)
class Magazine(models.Model):
managers = models.ForeignKey(MagazineUser)
# admin.py
class MagazineAdmin(admin.ModelAdmin):
def queryset(self, request):
qs = super(admin.ModelAdmin, self).queryset(request)
if request.user.is_superuser:
return qs
user_qs = MagazineUser.objects.filter(user=request.user)
return qs.filter(managers__in=user_qs)
|
How to convert string to datetime in python
Question: I have a date string in following format 2011-03-07 how to convert this to
datetime in python?
Answer: Try the following code, which uses `strptime` from the [datetime
module](http://docs.python.org/library/datetime.html):
from datetime import datetime
datetime.strptime('2011-03-07','%Y-%m-%d')
I note that this (and many other solutions) are trivially easy to find with
Google ;)
|
what is the type of the variable
Question: I am a very newbie in Python I have the folllowing code :
from SOAPpy import WSDL
fichier_wsdl = 'http://geocoder.us/dist/eg/clients/GeoCoder.wsdl'
wsdl = WSDL.Proxy(fichier_wsdl)
callInfo = wsdl.methods['geocode']
ss = wsdl.geocode('1600 Pennsylvania Ave, Washington, DC.')
print(ss)
The result is :
IMPORT: http://schemas.xmlsoap.org/soap/encoding/
no schemaLocation attribute in import
<<class 'SOAPpy.Types.typedArrayType'> results at 21824752>: [<SOAPpy.Types.structType item at 21818984>: {'city': 'Washington', 'prefix': '', 'suffix': 'NW', 'zip': 20502, 'number': 1600, 'long': -77.037684, 'state': 'DC', 'street': 'Pennsylvania', 'lat': 38.898748, 'type': 'Ave'}]
and I try to understand what type has my ss variable (the print(type(ss)) get
SOAPpy.Types.typedArrayType wich is not very clear for me) ? And how to have a
simple variable, for the city or the street ?
Answer: You can just do `type(variable name)`.
|
Mechanize not logging in to site properly
Question: After spending the best part of 3 hours getting nowhere, i thought i would ask
a question myself. i am using python and `mechanize`'s `Browser`. I am trying
to login to my home router. i can get to the login page, fill the password
field (eg `br.form['password'] = 'mypassword'` etc), but now i am stuck
because no matter what i try, i always get sent to a page saying i am
forbidden/session has timed out i am handling cookies with a cookie jar, i
have handled robots, but it still doesnt love me enough to let me login....
help? if you have any suggestions as to why i can not login successfully,
please, please, please share xxx
**EDIT:**
it does have javascript, but i am simulating it
**EDIT2:**
i just realized that the javascript i am simulating is for pressing the
disconnect button on the previous page...... probably fix my problem if i
emulate the javascript for this page ......
i am faking the user agent
i will have a look w/ wireshark xxx
ps thanks for replying so fast xx
UPDATE: sigh. i think it may just be one of those things where you just have
to say f it and move on because i am emulating the javascript it needed
exactly as it is done (just checking, MD5 ==
hashlib.md5("...").hexdigest()?).... thanks anyway people xxx
Answer: Here's some sample code for mechanize implementing cookies and a fake user-
agent -- might help out...
import mechanize
cookies = mechanize.CookieJar()
opener = mechanize.build_opener(mechanize.HTTPCookieProcessor(cookies))
opener.addheaders = [("User-agent", "Mozilla/5.0 (Macintosh; U; Intel Mac OS X 10_6; en-us) AppleWebKit/533.4 (KHTML, like Gecko) Version/4.1 Safari/533.4"),]
mechanize.install_opener(opener)
url = "http://your_home_router_address"
content = mechanize.urlopen(url)
return content.read()
|
How to take the first N items from a generator or list in Python?
Question: With [linq](/questions/tagged/linq "show questions tagged 'linq'") I would
var top5 = array.Take(5);
How to do this with Python?
Answer: # Slicing a list
top5 = array[:5]
* To slice a list, there's a simple syntax: `array[start:stop:step]`
* You can omit any parameter. These are all valid: `array[start:]`, `array[:stop]`, `array[::step]`
# Slicing a generator
import itertools
top5 = itertools.islice(my_list, 5) # grab the first five elements
* You can't slice a generator directly in Python. [`itertools.islice()`](http://docs.python.org/library/itertools.html#itertools.islice) will wrap an object in a new slicing generator using the syntax `itertools.islice(generator, start, stop, step)`
* Remember, slicing a generator will exhaust it partially. If you want to keep the entire generator intact, perhaps turn it into a tuple or list first, like: `result = tuple(generator)`
|
Persistent ssh session to Cisco router
Question: I have search on this site and multiple other locations but I have been unable
to resolve my problem of connecting and maintaining ssh session after one
command. Below is my current code:
#!/opt/local/bin/python
import os
import pexpect
import paramiko
import hashlib
import StringIO
while True:
cisco_cmd = raw_input("Enter cisco router cmd:")
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('192.168.221.235', username='nuts', password='cisco', timeout = 30)
stdin, stdout, stderr = ssh.exec_command(cisco_cmd)
print stdout.read()
ssh.close()
if cisco_cmd == 'exit': break
I can run multiple commands but for every commands a new ssh session is
created. The above program does not work when I need to configuration mode
because ssh session is not reused.Any assistance in resolving this matter is
greatly appreciated.
Answer: I used Exscript instead of paramiko and I am now able to get persistent
session on IOS device.
#!/opt/local/bin/python
import hashlib
import Exscript
from Exscript.util.interact import read_login
from Exscript.protocols import SSH2
account = read_login() # Prompt the user for his name and password
conn = SSH2() # We choose to use SSH2
conn.connect('192.168.221.235') # Open the SSH connection
conn.login(account) # Authenticate on the remote host
conn.execute('conf t') # Execute the "uname -a" command
conn.execute('interface Serial1/0')
conn.execute('ip address 114.168.221.202 255.255.255.0')
conn.execute('no shutdown')
conn.execute('end')
conn.execute('sh run int Serial1/0')
print conn.response
conn.execute('show ip route')
print conn.response
conn.send('exit\r') # Send the "exit" command
conn.close() # Wait for the connection to close
|
Boost python linking
Question: I'm adding boost.python for my Game. I write wrappers for my classes to use
them in scripts. The problem is linking that library to my app. I'm using
`cmake` build system.
Now I have a simple app with 1 file and makefile for it:
PYTHON = /usr/include/python2.7
BOOST_INC = /usr/include
BOOST_LIB = /usr/lib
TARGET = main
$(TARGET).so: $(TARGET).o
g++ -shared -Wl,--export-dynamic \
$(TARGET).o -L$(BOOST_LIB) -lboost_python \
-L/usr/lib/python2.7/config -lpython2.7 \
-o $(TARGET).so
$(TARGET).o: $(TARGET).cpp
g++ -I$(PYTHON) -I$(BOOST_INC) -c -fPIC $(TARGET).cpp
And this works. It builds a 'so' file for me which I can import from python.
Now the question: how to get this for cmake?
I wrote in main `CMakeList.txt`:
...
find_package(Boost COMPONENTS filesystem system date_time python REQUIRED)
message("Include dirs of boost: " ${Boost_INCLUDE_DIRS} )
message("Libs of boost: " ${Boost_LIBRARIES} )
include_directories(
${Boost_INCLUDE_DIRS}
...
)
target_link_libraries(Themisto
${Boost_LIBRARIES}
...
)
...
`message` calls show:
Include dirs of boost: /usr/include
Libs of boost: /usr/lib/libboost_filesystem-mt.a/usr/lib/libboost_system-mt.a/usr/lib/libboost_date_time-mt.a/usr/lib/libboost_python-mt.a
Ok, so I've added simple .cpp-file for my project with include of
`<boost/python.hpp>`. I get an error at compiling:
/usr/include/boost/python/detail/wrap_python.hpp:50:23: fatal error: pyconfig.h: No such file or directory
So it doesn't take all need include directories.
And **second** question:
How to organize 2-step building of script-cpp files? In makefile I showed
there are **TARGET.o** and **TARGET.so** , how to process that 2 commands in
cmake?
As I understand, the best way is to create subproject and do something there.
Thanks.
Answer: You are missing your include directory and libs for python in your
CMakeList.txt. Use the PythonFindLibs macro or the same find_package strategy
you used for Boost
find_package(Boost COMPONENTS filesystem system date_time python REQUIRED)
message("Include dirs of boost: " ${Boost_INCLUDE_DIRS} )
message("Libs of boost: " ${Boost_LIBRARIES} )
find_package(PythonLibs REQUIRED)
message("Include dirs of Python: " ${PYTHON_INCLUDE_DIRS} )
message("Libs of Python: " ${PYTHON_LIBRARIES} )
include_directories(
${Boost_INCLUDE_DIRS}
${PYTHON_INCLUDE_DIRS} # <-------
...
)
target_link_libraries(Themisto
${Boost_LIBRARIES}
${PYTHON_LIBRARIES} # <------
...
)
...
|
Help re-write this Python into Ruby: AJAX POST, decode Base-64, and save
Question: I'm following a phonegap tutorial and I do not know how to write this "def
iphone_upload " action in ruby 1.9.2/rails 3.
<http://wiki.phonegap.com/w/page/18270855/Image-Upload-using-JQuery-and-
Python>
function getPicture_Success(imageData)
{
var feedURL = APIPATH + "photos/iphone-upload/";
$.post(feedURL, {imageData:imageData}, function(data){
});
}
In Python (Django):
def iphone_upload(request):
import base64
data = base64.b64decode(request.POST.get("imageData"))
fileout = "/var/www/test.jpg"
f1 = open(fileout,'wb+')
f1.write(data)
f1.close()
Answer:
def iphone_upload
@data = request.POST[:imageData].unpack("m")[0]
fileout = "/var/www/test.jpg"
File.open(fileout, 'w') {|f| f.write(@data) }
end
|
why isn't this python regex statement returning my viewstate information?
Question:
def ExtractViewState(string):
m = re.match("__viewstate[^>]+value=\"\(\?<Value>[^\"]*\)", string, re.IGNORECASE)
return m.group(0)
I think I'm missing something, but it m keeps returning None. Blagh.
UPDATE:
<input type="hidden" name="__VIEWSTATE" value="5vzj+3s4pEHFJUQoOJbZicZdf+k2bi0uiXeIxMNTxjocu0FLzTXEI8pEcQy/V4r1vtIP6G/E0/j0C5TwvhaWdW1wJVGwGKfO26gvQk9O0zsxy5NBpx+PlfL5h7nlnAp+GmAIwdjLWxRFFbhxaOfH+yZQKfkzshBvE7xogxrTnrrlF22BiENHdWHuMqeGYb4AUfvbbJ2psQOwTTOF6meAjszLtaAxBVTgun4gVsGOKUDqasgzyYn7AsxsJ4rJ3S/64YU2sUwAsvCD1d0X3Q8bGiwriRU/pAo31xn4SfhP8dk22QbhFbVpvIwl3WGTxohL" />
should just return the text between in the value attribute:
"5vzj+3s4pEHFJUQoOJbZicZdf+k2bi0uiXeIxMNTxjocu0FLzTXEI8pEcQy/V4r1vtIP6G/E0/j0C5TwvhaWdW1wJVGwGKfO26gvQk9O0zsxy5NBpx+PlfL5h7nlnAp+GmAIwdjLWxRFFbhxaOfH+yZQKfkzshBvE7xogxrTnrrlF22BiENHdWHuMqeGYb4AUfvbbJ2psQOwTTOF6meAjszLtaAxBVTgun4gVsGOKUDqasgzyYn7AsxsJ4rJ3S/64YU2sUwAsvCD1d0X3Q8bGiwriRU/pAo31xn4SfhP8dk22QbhFbVpvIwl3WGTxohL"
Answer: You have a few issues:
import re
def ExtractViewState(string):
# re.match looks only at the **beginning** of the string
# dont escape the `( .. )` those capture the group
m = re.search("__viewstate[^>]+value=\"([^\"]*)", string, re.IGNORECASE)
# group(0) is the whole match, you want the 1st capture group
return m.group(1)
|
Python function to make arbitrary strings valid filenames
Question: Is there a built-in function which strips all characters which cannot be in
Windows filenames from a string or replaces them somehow?
E.g. `function("Some:unicode\symbols")` \--> `"Some-unicode-symbols"`
Answer:
import re
arbitrary_string = "File!name?.txt"
cleaned_up_filename = re.sub(r'[/\\:*?"<>|]', '', arbitrary_string)
filepath = os.path.join("/tmp", cleaned_up_filename)
with open(filepath, 'wb') as f:
# ...
Taken from User [gx](http://stackoverflow.com/users/21580/gx)
Obviously adapt to your situation.
|
fcntl.flock - how to implement a timeout?
Question: I am using python 2.7
I want to create a wrapper function around fcntl.flock() that will timeout
after a set interval:
wrapper_function(timeout):
I've tried calling on another thread and using thread.join(timeout) but it
seems that fcntl.flock() continues blocking:
def GetLock(self, timeout):
"""Returns true if lock is aquired, false if lock is already in use"""
self.__lock_file = open('proc_lock', 'w')
def GetLockOrTimeOut():
print 'ProcessLock: Acquiring Lock'
fcntl.flock(self.__lock_file.fileno(), fcntl.LOCK_EX)
print 'ProcessLock: Lock Acquired'
thread = threading.Thread(target=GetLockOrTimeOut)
thread.start()
thread.join(timeout)
if thread.isAlive():
print 'GetLock timed out'
return False
else:
return True
I've looked into solutions for terminating threads, the most popular solution
seems to be sub-classing threading.thread and adding a feature to raise an
exception in the thread. However, I came across a
[link](http://sebulba.wikispaces.com/recipe+thread2) that says this method
will not work with native calls, which I am pretty sure fcntl.flock() is
calling a native function. Suggestions?
Context: I am using a file-lock to create a single instance application but I
don't want a second instance of the application to sit around and hang until
the first instance terminates.
Answer: Timeouts for system calls are done with signals. Most blocking system calls
return with EINTR when a signal happens, so you can use `alarm` to implement
timeouts.
Here's a context manager that works with most system calls, causing IOError to
be raised from a blocking system call if it takes too long.
import signal, errno
from contextlib import contextmanager
import fcntl
@contextmanager
def timeout(seconds):
def timeout_handler(signum, frame):
pass
original_handler = signal.signal(signal.SIGALRM, timeout_handler)
try:
signal.alarm(seconds)
yield
finally:
signal.alarm(0)
signal.signal(signal.SIGALRM, original_handler)
with timeout(1):
f = open("test.lck", "w")
try:
fcntl.flock(f.fileno(), fcntl.LOCK_EX)
except IOError, e:
if e.errno != errno.EINTR:
raise e
print "Lock timed out"
|
Equation solver in Python
Question: Given a simple equation such as:
x = y + z
You can get the third variable if you bind the other two (ie: `y = x - z` and
`z = x - y`). A straightforward way to put this in code:
def solve(args):
if 'x' not in args:
return args['y'] + args['z']
elif 'z' not in args:
return args['x'] - args['y']
elif 'y' not in args:
return args['x'] - args['z']
else:
raise SomeError
I obviously can take an equation, parse it and simplify it to achieve the same
effect. But I believe in doing so I would be re-inventing the wheel. So
where's my ready-made wheel?
Answer: Consider using [Sympy](http://code.google.com/p/sympy/). It includes various
tools to solve equations and a lot more.
The following is an excerpt from the
[docs](http://docs.sympy.org/dev/modules/solvers/solvers.html):
>>> from sympy import I, solve
>>> from sympy.abc import x, y
>>> solve(x**4-1, x)
[1, -1, -I, I]
|
How to see the real SQL query in Python cursor.execute
Question: I use the following code in Python (with pyodbc for a MS-Access base).
cursor.execute("select a from tbl where b=? and c=?", (x, y))
It's Ok but, for maintenance purposes, I need to know the complete and exact
SQL string send to the database.
Is it possible and how ?
Answer: It differs by driver. Here are two examples:
import MySQLdb
mc = MySQLdb.connect()
r = mc.cursor()
r.execute('select %s, %s', ("foo", 2))
r._executed
"select 'foo', 2"
import psycopg2
pc = psycopg2.connect()
r = pc.cursor()
r.execute('select %s, %s', ('foo', 2))
r.query
"select E'foo', 2"
|
Website to image
Question: I'm running Python 3.1 and you would call me an advanced novice :)
My question is simple: I'm trying to make a simple program which asks the
users for a URL (or multiple URLs) and then goes to the website and takes a
screenshot (of the whole page, not just what can be seen in the browser
without scrolling all the way down).
It's simpler then it sounds, I want to use an existing platform on the web,
similar to this:
import subprocess
MYFILENAME = "google_screen"
MYURL = "www.google.com"
subprocess.Popen(['wget', '-O', MYFILENAME+'.png', 'http://images.websnapr.com/?url='+MYURL+'&size=s&nocache=82']).wait()
Although this website does not work :(, I'm wondering is it possible to do it
with [this website](http://www.sciweavers.org/free-online-web-to-image) and if
so, how? If it is not possible, are there any alternatives?
Answer: There is a package called webkit2png that you can use for this, its located:
[here](https://github.com/paulhammond/webkit2png/)
More information on [this blog
post](http://rolandtapken.de/blog/2008-12/create-screenshots-web-page-using-
python-and-qtwebkit)
Example from blog post(copied to SO for preservation, read the blog post to
understand it if you have issues):
#!/usr/bin/env python
import sys
import signal
from PyQt4.QtCore import *
from PyQt 4.QtGui import *
from PyQt4.QtWebKit import QWebPage
def onLoadFinished(result):
if not result:
print "Request failed"
sys.exit(1)
# Set the size of the (virtual) browser window
webpage.setViewportSize(webpage.mainFrame().contentsSize())
# Paint this frame into an image
image = QImage(webpage.viewportSize(), QImage.Format_ARGB32)
painter = QPainter(image)
webpage.mainFrame().render(painter)
painter.end()
image.save("output2.png")
sys.exit(0)
app = QApplication(sys.argv)
signal.signal(signal.SIGINT, signal.SIG_DFL)
webpage = QWebPage()
webpage.connect(webpage, SIGNAL("loadFinished(bool)"), onLoadFinished)
webpage.mainFrame().load(QUrl("http://www.google.com"))
sys.exit(app.exec_())
Edit: [Link to the pyqt4 download
page](http://www.riverbankcomputing.co.uk/software/pyqt/download)
|
Comparing Strings
Question: Does there exist any inbuilt function in python than can return number of
mathching characters in two strings,for example:
INPUT:
TICK TOCK
CAT DOG
APPLE APPLES
OUTPUT:
3
0
5
The words "TICK" and "TOCK" have a score of 3, since three characters (T, C,
K) are the same. Similarly, "CAT" and "DOG" score 0, since no letters match.
I am a new bie in python so please help me with examples.
Answer: Here's a version using list comprehensions:
[x == y for (x, y) in zip("TICK", "TOCK")].count(True)
Or, shorter (using `operator`):
import operator
map(operator.eq, "TICK", "TOCK").count(True)
According to @Kabie, `<expr>.count(True)` can be replaced by `sum(<expr>)` in
both versions.
|
Getting confirmation window with Selenium-rc
Question: I'm running a selenium server (v.2.0b2) and writing a python script to run a
test suite on my webapp.
from selenium import webdriver
import selenium
selenium = selenium.selenium('127.0.0.1', 3333, '*firefox', 'http://localhost/')
selenium.start()
profile = webdriver.FirefoxProfile('selenium')
browser = webdriver.Firefox(profile)
browser.get('http://localhost:8080/index.html?no_auto_login=1')
I have a login button that pops up a confirmation dialog, but it takes a round
trip the the server and back before it pops up.
submit_button = browser.find_element_by_css_selector('#btnSubmit')
submit_button.click()
alert = browser.switch_to_alert()
assert alert.text == 'Server Login Error...'
alert.accept()
commenting out the items after submit_button.click() and then calling
selenium.is_confirmation_present() returns false
How can I wait for the confirmation box to be visible? Why doesn't
selenium.is_confirmation_present() return true?
Answer: I have not worked with Selenium 2.0 (web driver) but would suggest you to test
this with Thread.sleep(10). And if that works then it means conditional wait
in required in your case.
|
In python, how do I get timing information like os.times() for a specific child process?
Question: I can use os.times or resource.getrlimit to get user time of the current
process, all the children processes, or both.
How do I get timing information for a specific child process?
Answer: I don't know if you can do this in general, but on Linux you can just parse
`/proc/<PID>/stat` to find the first four values that you would get from
`os.times` for any process. For example:
import sys
import os
if not len(sys.argv) == 2:
print >> sys.stderr, "Usage: %s <PID>" % (sys.argv[0])
sys.exit(1)
pid = int(sys.argv[1])
hz = os.sysconf(os.sysconf_names['SC_CLK_TCK'])
with open("/proc/%d/stat" % (pid,)) as fp:
fields = fp.read().split(' ')[13:17]
utime, stime, cutime, cstime = [ (float(f) / hz) for f in fields ]
print "utime in clock ticks:", utime
print "stime in clock ticks:", stime
print "cutime in clock ticks:", cutime
print "cstime in clock ticks:", cstime
Presumably you have the process IDs of the child processes you're interested
in.
I found out how to get the value of `sysconf(_SC_CLK_TCK)` from this question:
[Python: How to get number of mili seconds per
jiffy](http://stackoverflow.com/questions/4189123/python-how-to-get-number-of-
mili-seconds-per-jiffy/4189612#4189612) and the information about the fields
in `/proc/<PID>/stat` is from the `proc(5)` man page.
|
How to spawn Python2.5 process through Apache and return immediately under Windows
Question: I have two Python scripts, one launches the other with subprocess
invoke.py:
import subprocess
p = subprocess.Popen(['python', 'long.py'])
print "Content-Type: text/plain\n"
print "invoked (%d)" % (p.pid)
longtime.py:
import time
import os
print "start (%d)" %(os.getpid())
time.sleep(10)
print "end (%d)" %(os.getpid())
When I execute invoke.py from shell it returns immediately and longtime.py
works in background (works on Windows and Linux). If I call invoke.py through
Web Interface (Apache CGI) it works under Linux **but not on Windows**
machine, there the website gets stuck and only returns after longtime.py has
finished.
How can I configure Python subprocess or Apache to get the same behavior under
Windows? Whats the difference?
Maybe the Apache config on Windows is somehow different but i didnt find
something.
Linux: Debian, Python2.5.2, Apache2.2.9
Windows: WinXP, Python2.7, Apache2.2.17
Maybe you have also a better design approach (because its a little awkward how
I do it now).
What for?: I have a script on the webserver which takes quite a long time to
calculate (longtime.py). I want to activate the execution via web interface.
The Website should return immediatly and longtime.py should work in background
and writes output in a file. Later a request from web interface checks if the
file is generated and reads the output. I can not use common cloud-provider as
they dont support multithreading. Also I can not install a daemon handler on
the webserver because processes have a maximum runtime.
Answer: I've tested the code below on Windows XP and on OSX 10.6.6 (shell) and it
exits without waiting for the child process to finish.
**invoke.py:**
from subprocess import Popen, PIPE
import platform
if platform.system() == 'Windows':
close_fds=False
else:
close_fds=True
p = Popen('python long.py', stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=close_fds, shell=True)
print "Content-Type: text/plain\n"
print "invoked (%d)" % (p.pid)
**long.py**
import time
import os
print "start (%d)" %(os.getpid())
time.sleep(10)
print "end (%d)" %(os.getpid())
**Update:** Tested on Windows 7 + Apache 2.2.17 + Python 2.7 + mod_wsgi 3.3.
mod_wsgi.so file can be downloaded from
[here](http://code.google.com/p/modwsgi/wiki/DownloadTheSoftware?tm=2). File
should be renamed to mod_wsgi.so and and placed in apache modules folder.
**invoke.wsgi:** from subprocess import Popen, PIPE import platform
def application(environ, start_response):
if platform.system() == 'Windows':
close_fds=False
else:
close_fds=True
p = Popen('python "C:\testing\long.py"', stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=close_fds, shell=True)
status = '200 OK'
output = "invoked (%d)" % (p.pid)
response_headers = [('Content-type', 'text/plain'), ('Content-Length', str(len(output)))]
start_response(status, response_headers)
return [output]
**long.py** file was left unchanged.
changes made to **httpd.conf** :
append wsgi module:
LoadModule wsgi_module modules/mod_wsgi.so
add directory to the config
<Directory "C:/testing">
AllowOverride None
Options None
Order allow,deny
Allow from all
</Directory>
link url with directory
Alias /testapp "C:\testing"
link url with wsgi app
WSGIScriptAlias /testapp "C:\testing\invoke.wsgi"
Restart web server. Go <http://server_name/testapp> App should show process id
and exit.
|
Is there a way to access parent modules in Python
Question: I need to know if there is a way to access parent modules from submodules. If
I import submodule:
from subprocess import types
I have `types` \- is there some Python magic to get access to `subprocess`
module from `types`? Something similar to this for classes
`().__class__.__bases__[0].__subclasses__()`.
Answer: If you've accessed a module you can typically get to it from the `sys.modules`
dictionary. Python doesn't keep "parent pointers" with names, particularly
because the relationship is not one-to-one. For example, using your example:
>>> from subprocess import types
>>> types
<module 'types' from '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/types.pyc'>
>>> import sys
>>> sys.modules['subprocess']
<module 'subprocess' from '/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/subprocess.pyc'>
If you'll note the presence of `types` in the `subprocess` module is just an
artifact of the `import types` statement in it. You just `import types` if you
need that module.
In fact, a future version of `subprocess` may not import `types` any more, and
your code will break. You should only import the names that appear in the
`__all__` list of a module; consider other names as implementation details.
So, for example:
>>> import subprocess
>>> dir(subprocess)
['CalledProcessError', 'MAXFD', 'PIPE', 'Popen', 'STDOUT', '_PIPE_BUF', '__all__', '__builtins__', '__doc__',
'__file__', '__name__', '__package__', '_active', '_cleanup', '_demo_posix', '_demo_windows', '_eintr_retry_call',
'_has_poll', 'call', 'check_call', 'check_output', 'errno', 'fcntl', 'gc', 'list2cmdline', 'mswindows', 'os',
'pickle', 'select', 'signal', 'sys', 'traceback', 'types']
>>> subprocess.__all__
['Popen', 'PIPE', 'STDOUT', 'call', 'check_call', 'check_output', 'CalledProcessError']
You can see that most of the names visible in `subprocess` are just other top-
level modules that it imports.
|
mocking functions using python mock
Question: I am trying to Mock a function (that returns some external content) using the
python mock module (http://www.voidspace.org.uk/python/mock/index.html).
I'm having some trouble mocking functions that are imported into a module.
For example, in util.py I have
def get_content():
return "stuff"
I want to mock util.get_content so that it returns something else.
I am trying this:
util.get_content=Mock(return_value="mocked stuff")
If `get_content` gets invoked inside another module, it never actually seems
to return the mocked object. Am I missing something in terms of how to use
Mock?
Note that if I invoke the following, things work correctly:
>>> util.get_content=Mock(return_value="mocked stuff")
>>> util.get_content()
"mocked stuff"
However, if get_content is called from inside another module, it invokes the
original function instead of the mocked version:
>>> from mymodule import MyObj
>>> util.get_content=Mock(return_value="mocked stuff")
>>> m=MyObj()
>>> m.func()
"stuff"
Contents of mymodule.py
from util import get_content
class MyObj:
def func():
get_content()
So I guess my question is - how do I get invoke the Mocked version of a
function from inside a module that I call?
It appears that the `from module import function` may be to blame here, in
that it doesn't point to the Mocked function.
Answer: I think I have a workaround, though I'm still not quite clear on how to solve
the general case
In mymodule, if I replace
from util import get_content
class MyObj:
def func():
get_content()
with
import util
class MyObj:
def func():
util.get_content()
The Mock seems to get invoked. Looks like the namespaces need to match (which
makes sense). However, the weird thing is that I would expect
import mymodule
mymodule.get_content = mock.Mock(return_value="mocked stuff")
to do the trick in the original case where I am using the from/import syntax
(which now pulls in get_content into mymodule). But this still refers to the
unmocked get_content.
Turns out the namespace matters - just need to keep that in mind when writing
your code.
|
mod_wsgi cannot load mysql
Question: First I will list my environment and status:
Environment:
* System: Mac OS 10.6
* Python: 2.6
* Apache: 2.2
* mod_wsgi: 3.3
* mysql: 5.x
* php: 3.5
* trac:0.12
Status: I can run trac as alone-server without problem. Now I integrate trac
to apache, problem come out. mod_wsgi can run normal wsgi page correctly, but
cannot load mysql connection. I test it in piece of code, put "**import
MySQLdb** " in wsgi page, it still cannot. I also can access trac through
apache, but it shows me **Cannot load Python bindings for MySQL**
I refer to the apache log:
[Sun Mar 13 13:36:44 2011] [error] [client ::1] mod_wsgi (pid=37060): Target WSGI script /Users/alex/Library/apache2/htdocs/sql.wsgi' cannot be loaded as Python module.
[Sun Mar 13 13:36:44 2011] [error] [client ::1] mod_wsgi (pid=37060): Exception occurred processing WSGI script '/Users/alex/Library/apache2/htdocs/sql.wsgi'.
[Sun Mar 13 13:36:44 2011] [error] [client ::1] Traceback (most recent call last):
[Sun Mar 13 13:36:44 2011] [error] [client ::1] File "/Users/alex/Library/apache2/htdocs/sql.wsgi", line 2, in <module>
[Sun Mar 13 13:36:44 2011] [error] [client ::1] import MySQLdb
[Sun Mar 13 13:36:44 2011] [error] [client ::1] File "build/bdist.macosx-10.6-universal/egg/MySQLdb/__init__.py", line 19, in <module>
[Sun Mar 13 13:36:44 2011] [error] [client ::1] File "build/bdist.macosx-10.6-universal/egg/_mysql.py", line 7, in <module>
[Sun Mar 13 13:36:44 2011] [error] [client ::1] File "build/bdist.macosx-10.6-universal/egg/_mysql.py", line 6, in __bootstrap__
[Sun Mar 13 13:36:44 2011] [error] [client ::1] ImportError: dlopen(/Users/alex/.python-eggs/MySQL_python-1.2.3-py2.6-macosx-10.6-universal.egg-tmp/_mysql.so, 2): Library not loaded: libmysqlclient.16.dylib
[Sun Mar 13 13:36:44 2011] [error] [client ::1] Referenced from: /Users/alex/.python-eggs/MySQL_python-1.2.3-py2.6-macosx-10.6-universal.egg-tmp/_mysql.so
[Sun Mar 13 13:36:44 2011] [error] [client ::1] Reason: image not found
[Sun Mar 13 13:36:57 2011] [error] [client ::1] mod_wsgi (pid=37061): Target WSGI script
This looks like mod_wsgi cannot find libmysqlclient.16.dylib. I encounter
similar problem when I install mysqldb for python, so I add export
`DYLD_LIBRARY_PATH=/Users/alex/Library/mysql-5.x/lib`
SO python -c "import MySQLdb" can work, but mod_wsgi cannot work. So I put
os.environ['DYLD_LIBRARY_PATH'] = '/Users/alex/Library/mysql-5.x/lib'
into trac.ini. It doesn't work for trac in apache still.
So anyone has this problem before? Thanks
Answer: Try **LD_LIBRARY_PATH** instead:
export LD_LIBRARY_PATH=/usr/local/mysql/lib/mysql:$LD_LIBRARY_PATH
|
Regular Expression and escape sequences
Question: I have a file which contains the list of regular expressions to look for in
db.
one such pattern is `(/|\)cmd\.com$`. But when i use it with re module, it
throws up the below error. If i use the re pattern as `(/|\\\\)cmd\.com$`,it
works.
So, the question is when i read from a file in to variable for EX: a, how do i
convert it to a reg pattern with four backward slashes so that it starts
working with python re module.
Also, how do we escape such escape sequences when reg pattern is assigned to a
variable EX: "a" below.
Any help on this is appreciated.
import re
a='(/|\)cmd\.com$'
re.compile(a)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.6/re.py", line 190, in compile
return _compile(pattern, flags)
File "/usr/lib/python2.6/re.py", line 245, in _compile
raise error, v # invalid expression
sre_constants.error: unbalanced parenthesis
Thx, Santhosh
Answer: First note that your original regex is invalid. It should be
`(/|\\)cmd\.com$`. If such a string is coming from a database (or any other
source other than a string literal in your code), then no additional
manipulation needs to be done before the regex engine sees it -- the slashes
are correct.
Full details and explanation:
Backslashes are special in that they escape other characters and give them
different meanings.
a = '(/|\)cmd\.com$'
In this regular expression, the `)` is special, indicating the end of a
grouping expression; the backslash escapes it to make it interpreted as a
literal `)` instead, which is not what you want (and why you get the error
about mismatched parentheses).
You need to escape the backslash to make it be interpreted as a literal `\`;
this can be done using yet another backslash:
a = '(/|\\)cmd\.com$'
However even this will not work, since in Python there are two levels of
processing going on (and thus two levels of escaping are needed): First, the
string literal is evaluated, and the backslashes are interpreted specially
(string-wise, where e.g. `\.` is not meaningful, and so evaluates to `\.` \--
however `\\` evaluates to `\`). Then, when the regex engine gets the string,
it interprets any literal backslashes in _that_ object specially (regex-wise,
e.g. `\.` makes the `.` literal instead of "any character"). So you end up
with:
a = '(/|\\\\)cmd\\.com$' # Escaped version of (/|\\)cmd\.com$ which is what regex engine will see
Because this problem is so common, Python has a way of writing strings such
that the backslash is _not_ treated specially in the string-processing stage:
["raw" string
literals](http://docs.python.org/reference/lexical_analysis.html#string-
literals):
a = r'(/|\\)cmd\.com$' # backslashes here will be interpreted as literal \ characters
The regex engine will still interpret the backslashes in the string specially
(a raw string is just a way of writing the literal; it still results in a
plain `str` object).
|
Can I write to terminal and a given file with one command in Python?
Question: I have seen this question answered in reference to Bash, but can't find one
for Python. Apologies if this is repeating something.
Is it possible to print to the terminal and an output file with one command?
I'm familiar with using `print >>` and `sys.stdout = WritableObject`, but I'd
like to avoid having to double print commands for each line I want logged.
I'm using Python 2.6, just in case such knowledge is necessary.
More importantly, I want this to run on a Windows-based system using IDLE's
command line. So, in essence, I want the python script to report to IDLE's
terminal and a given log file.
**EDIT** : For anyone who finds this and decides to go with the answer I
chose, if you need help understanding context managers (like I did), I
recommend Doug Hellman's Python Modules of the Week for clarification. [This
one details the context
library.](http://www.doughellmann.com/PyMOTW/contextlib/index.html "This one
details context managers.") For help with decorators [see this Stack Overflow
question's answers.](http://stackoverflow.com/questions/739654/understanding-
python-decorators)
Answer: Replace `sys.stdout`.
class PrintAndLog(object):
def __init__(self, fileOrPath): # choose which makes more sense
self._file = ...
def write(s):
sys.stdout.write(s)
self._file.write(s)
def close(self):
self._file.close()
# insert wrappers for .flush, .writelines
_old_stdout = sys.stdout
sys.stdout = PrintAndLog(f)
... # print and stuff
sys.stdout = _old_stdout
Can be put into a context manager (this is at least the third time I see
something like this on SO alone...):
from contextlib import contextmanager
@contextmanager
def replace_stdout(f):
old_stdout = sys.stdout
try:
sys.stdout = PrintAndLog(f)
yield
finally:
sys.stdout = old_stdout
|
How to save new data in tree model view
Question: I'm trying to modify the excellent example of pyqt4 called "Editabletreemodel"
but I have a problem I can't manage: after I add a new row in the model, how
can I save or update the data I've inserted to a text file? Or more in
general, how is it possible to save data from the model/view into a file?
Thank you for your help.
# This is only needed for Python v2 but is harmless for Python v3.
import sip
sip.setapi('QVariant', 2)
from PyQt4 import QtCore, QtGui
import editabletreemodel
from ui_mainwindow import Ui_MainWindow
import sys, os, time
import paramiko
import threading
class TreeItem(object):
def __init__(self, data, parent=None):
self.parentItem = parent
self.itemData = data
self.childItems = []
def child(self, row):
return self.childItems[row]
def childCount(self):
return len(self.childItems)
def childNumber(self):
if self.parentItem != None:
return self.parentItem.childItems.index(self)
return 0
def columnCount(self):
return len(self.itemData)
def data(self, column):
return self.itemData[column]
def insertChildren(self, position, count, columns):
if position < 0 or position > len(self.childItems):
return False
for row in range(count):
data = [None for v in range(columns)]
item = TreeItem(data, self)
self.childItems.insert(position, item)
return True
def insertColumns(self, position, columns):
if position < 0 or position > len(self.itemData):
return False
for column in range(columns):
self.itemData.insert(position, None)
for child in self.childItems:
child.insertColumns(position, columns)
return True
def parent(self):
return self.parentItem
def removeChildren(self, position, count):
if position < 0 or position + count > len(self.childItems):
return False
for row in range(count):
self.childItems.pop(position)
return True
def removeColumns(self, position, columns):
if position < 0 or position + columns > len(self.itemData):
return False
for column in range(columns):
self.itemData.pop(position)
for child in self.childItems:
child.removeColumns(position, columns)
return True
def setData(self, column, value):
if column < 0 or column >= len(self.itemData):
return False
self.itemData[column] = value
return True
class TreeModel(QtCore.QAbstractItemModel):
def __init__(self, headers, data, parent=None):
super(TreeModel, self).__init__(parent)
rootData = [header for header in headers]
self.rootItem = TreeItem(rootData)
self.setupModelData(data.split("\n"), self.rootItem)
def columnCount(self, parent=QtCore.QModelIndex()):
return self.rootItem.columnCount()
def data(self, index, role):
if not index.isValid():
return None
if role != QtCore.Qt.DisplayRole and role != QtCore.Qt.EditRole:
return None
item = self.getItem(index)
return item.data(index.column())
def flags(self, index):
if not index.isValid():
return 0
return QtCore.Qt.ItemIsEditable | QtCore.Qt.ItemIsEnabled | QtCore.Qt.ItemIsSelectable
def getItem(self, index):
if index.isValid():
item = index.internalPointer()
if item:
return item
return self.rootItem
def headerData(self, section, orientation, role=QtCore.Qt.DisplayRole):
if orientation == QtCore.Qt.Horizontal and role == QtCore.Qt.DisplayRole:
return self.rootItem.data(section)
return None
def index(self, row, column, parent=QtCore.QModelIndex()):
if parent.isValid() and parent.column() != 0:
return QtCore.QModelIndex()
parentItem = self.getItem(parent)
childItem = parentItem.child(row)
if childItem:
return self.createIndex(row, column, childItem)
else:
return QtCore.QModelIndex()
def insertColumns(self, position, columns, parent=QtCore.QModelIndex()):
self.beginInsertColumns(parent, position, position + columns - 1)
success = self.rootItem.insertColumns(position, columns)
self.endInsertColumns()
return success
def insertRows(self, position, rows, parent=QtCore.QModelIndex()):
parentItem = self.getItem(parent)
self.beginInsertRows(parent, position, position + rows - 1)
success = parentItem.insertChildren(position, rows,
self.rootItem.columnCount())
self.endInsertRows()
return success
def parent(self, index):
if not index.isValid():
return QtCore.QModelIndex()
childItem = self.getItem(index)
parentItem = childItem.parent()
if parentItem == self.rootItem:
return QtCore.QModelIndex()
return self.createIndex(parentItem.childNumber(), 0, parentItem)
def removeColumns(self, position, columns, parent=QtCore.QModelIndex()):
self.beginRemoveColumns(parent, position, position + columns - 1)
success = self.rootItem.removeColumns(position, columns)
self.endRemoveColumns()
if self.rootItem.columnCount() == 0:
self.removeRows(0, rowCount())
return success
def removeRows(self, position, rows, parent=QtCore.QModelIndex()):
parentItem = self.getItem(parent)
self.beginRemoveRows(parent, position, position + rows - 1)
success = parentItem.removeChildren(position, rows)
self.endRemoveRows()
return success
def rowCount(self, parent=QtCore.QModelIndex()):
parentItem = self.getItem(parent)
return parentItem.childCount()
def setData(self, index, value, role=QtCore.Qt.EditRole):
if role != QtCore.Qt.EditRole:
return False
item = self.getItem(index)
result = item.setData(index.column(), value)
if result:
self.dataChanged.emit(index, index)
return result
def setHeaderData(self, section, orientation, value, role=QtCore.Qt.EditRole):
if role != QtCore.Qt.EditRole or orientation != QtCore.Qt.Horizontal:
return False
result = self.rootItem.setData(section, value)
if result:
self.headerDataChanged.emit(orientation, section, section)
return result
def setupModelData(self, lines, parent):
parents = [parent]
indentations = [0]
number = 0
while number < len(lines):
position = 0
while position < len(lines[number]):
if lines[number][position] != " ":
break
position += 1
lineData = lines[number][position:].trimmed()
if lineData:
# Read the column data from the rest of the line.
columnData = [s for s in lineData.split('\t') if s]
if position > indentations[-1]:
# The last child of the current parent is now the new
# parent unless the current parent has no children.
if parents[-1].childCount() > 0:
parents.append(parents[-1].child(parents[-1].childCount() - 1))
indentations.append(position)
else:
while position < indentations[-1] and len(parents) > 0:
parents.pop()
indentations.pop()
# Append a new item to the current parent's list of children.
parent = parents[-1]
parent.insertChildren(parent.childCount(), 1,
self.rootItem.columnCount())
for column in range(len(columnData)):
parent.child(parent.childCount() -1).setData(column, columnData[column])
number += 1
class MainWindow(QtGui.QMainWindow, Ui_MainWindow):
def __init__(self, parent=None):
super(MainWindow, self).__init__(parent)
self.setupUi(self)
headers = ("Sendor Name", "Address", "Comments")
file = QtCore.QFile('./default.txt')
file.open(QtCore.QIODevice.ReadOnly)
model = TreeModel(headers, file.readAll())
file.close()
print model.invisibleRootItem()
self.view.setModel(model)
for column in range(model.columnCount(QtCore.QModelIndex())):
self.view.resizeColumnToContents(column)
self.exitAction.triggered.connect(QtGui.qApp.quit)
self.view.selectionModel().selectionChanged.connect(self.updateActions)
self.actionsMenu.aboutToShow.connect(self.updateActions)
self.insertRowAction.triggered.connect(self.insertRow)
self.insertColumnAction.triggered.connect(self.insertColumn)
self.removeRowAction.triggered.connect(self.removeRow)
self.removeColumnAction.triggered.connect(self.removeColumn)
self.insertChildAction.triggered.connect(self.insertChild)
self.callSensorsButton.clicked.connect(self.call_sensors)
self.updateActions()
self.view.expandAll()
self.view.setContextMenuPolicy(QtCore.Qt.CustomContextMenu)
self.view.customContextMenuRequested.connect(self.openMenu)
self.connection = connection_thread()
self.connect(self.connection, QtCore.SIGNAL("started()"), self.start_progressBar)
self.connect(self.connection, QtCore.SIGNAL("finished()"), self.stop_progressBar)
self.connect(self.connection, QtCore.SIGNAL("terminated()"), self.stop_progressBar)
self.SaveListButton.clicked.connect(self.save_sensor_list)
self.pushButton.clicked.connect(self.prova)
def save_sensor_list(self):
index = self.view.selectionModel().currentIndex()
model = self.view.model()
print model.rootItem
for i in range(0, model.rootItem.rowCount()):
print model.child(i)
def prova(self):
index = self.view.selectionModel().currentIndex()
model = self.view.model()
print model.data(index,0)
def openMenu(self, position):
indexes = self.view.selectedIndexes()
model = self.view.model()
if len(indexes) > 0:
level = 0
index = indexes[0]
while index.parent().isValid():
index = index.parent()
level += 1
menu = QtGui.QMenu()
if level == 0:
menu.addAction(self.tr("Call all %ss" % (model.data(index,0))))
menu.addSeparator()
menu.addAction(self.tr("Add new sensor family"),self.insertRow)
menu.addAction(self.tr("Add new sensor"),self.insertChild)
elif level == 1:
menu.addAction(self.tr("Call this sensor"))
menu.addSeparator()
menu.addAction(self.tr("Add new sensor"),self.insertRow)
elif level == 2:
menu.addAction(self.tr("Edit object"))
menu.exec_(self.view.viewport().mapToGlobal(position))
def insertChild(self):
index = self.view.selectionModel().currentIndex()
model = self.view.model()
if model.columnCount(index) == 0:
if not model.insertColumn(0, index):
return
if not model.insertRow(0, index):
return
for column in range(model.columnCount(index)):
child = model.index(0, column, index)
model.setData(child, "[No data]", QtCore.Qt.EditRole)
if not model.headerData(column, QtCore.Qt.Horizontal).isValid():
model.setHeaderData(column, QtCore.Qt.Horizontal,
"[No header]", QtCore.Qt.EditRole)
self.view.selectionModel().setCurrentIndex(model.index(0, 0, index),
QtGui.QItemSelectionModel.ClearAndSelect)
self.updateActions()
def insertColumn(self, parent=QtCore.QModelIndex()):
model = self.view.model()
column = self.view.selectionModel().currentIndex().column()
# Insert a column in the parent item.
changed = model.insertColumn(column + 1, parent)
if changed:
model.setHeaderData(column + 1, QtCore.Qt.Horizontal,
"[No header]", QtCore.Qt.EditRole)
self.updateActions()
return changed
def insertRow(self):
index = self.view.selectionModel().currentIndex()
model = self.view.model()
if not model.insertRow(index.row()+1, index.parent()):
return
self.updateActions()
for column in range(model.columnCount(index.parent())):
child = model.index(index.row()+1, column, index.parent())
model.setData(child, "[No data]", QtCore.Qt.EditRole)
def removeColumn(self, parent=QtCore.QModelIndex()):
model = self.view.model()
column = self.view.selectionModel().currentIndex().column()
# Insert columns in each child of the parent item.
changed = model.removeColumn(column, parent)
if not parent.isValid() and changed:
self.updateActions()
return changed
def removeRow(self):
index = self.view.selectionModel().currentIndex()
model = self.view.model()
if (model.removeRow(index.row(), index.parent())):
self.updateActions()
def updateActions(self):
hasSelection = not self.view.selectionModel().selection().isEmpty()
self.removeRowAction.setEnabled(hasSelection)
self.removeColumnAction.setEnabled(hasSelection)
hasCurrent = self.view.selectionModel().currentIndex().isValid()
self.insertRowAction.setEnabled(hasCurrent)
self.insertColumnAction.setEnabled(hasCurrent)
if hasCurrent:
self.view.closePersistentEditor(self.view.selectionModel().currentIndex())
row = self.view.selectionModel().currentIndex().row()
column = self.view.selectionModel().currentIndex().column()
if self.view.selectionModel().currentIndex().parent().isValid():
self.statusBar().showMessage("Position: (%d,%d)" % (row, column))
else:
self.statusBar().showMessage("Position: (%d,%d) in top level" % (row, column))
def start_progressBar(self):
self.progressBar.setRange(0,0)
self.progressBar.setValue(0)
def stop_progressBar(self):
self.progressBar.setRange(0,1)
self.progressBar.setValue(1)
def call_sensors(self):
self.textEdit.insertPlainText("Connecting to Fox...\n")
self.connection.start_thread(self.textEdit)
class connection_thread(QtCore.QThread):
def __init__(self, parent = None):
QtCore.QThread.__init__(self, parent)
def start_thread(self,textEdit):
self.textEdit = textEdit
self.start()
def run(self):
print "Dentro il thread"
time.sleep(10)
try:
ssh = paramiko.SSHClient()
ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
ssh.connect('192.168.0.90', username='root', password='netusg20')
self.textEdit.insertPlainText("Calling sensor list...\n")
app.processEvents()
stdin, stdout, stderr = ssh.exec_command('python g20.py c')
self.textEdit.insertPlainText(stdout.read())
self.textEdit.insertPlainText(stderr.read())
self.textEdit.insertPlainText("Connection closed\n")
ssh.close()
app.processEvents()
except:
self.textEdit.insertPlainText(str(sys.exc_info()[1]))
ssh.close()
app.processEvents()
if __name__ == '__main__':
app = QtGui.QApplication(sys.argv)
window = MainWindow()
window.show()
sys.exit(app.exec_())
Answer: I guess the easies way would be to iterate though model items and save save to
file via [QDataStream](http://doc.qt.nokia.com/latest/qdatastream.html).
QDataStream supports reading\writing QVariant's and you can get\set the model
item's data as [QVariant](http://doc.qt.nokia.com/4.7-snapshot/qvariant.html).
Below is a small example, I'm using
[QStandardItemModel](http://doc.qt.nokia.com/4.7.1/qstandarditemmodel.html)
for simplicity:
import sys
from PyQt4 import QtGui, QtCore
class MainForm(QtGui.QMainWindow):
def __init__(self, parent=None):
super(MainForm, self).__init__(parent)
self.setMinimumSize(400, 400)
# create model
self.model = QtGui.QStandardItemModel()
for k in range(0, 4):
parentItem = self.model.invisibleRootItem()
for i in range(0, 4):
item = QtGui.QStandardItem(QtCore.QString("item %0 %1").arg(k).arg(i))
parentItem.appendRow(item)
parentItem = item
# create treeview
self.view = QtGui.QTreeView(self)
self.view.setModel(self.model)
self.view.setMinimumSize(300, 400)
self.saveButton = QtGui.QPushButton("save", self)
self.saveButton.move(300, 1)
self.saveButton.clicked.connect(self.on_save_button_clicked)
self.layout = QtGui.QVBoxLayout(self.centralWidget())
self.layout.addWidget(self.view)
self.layout.addWidget(self.saveButton)
def on_save_button_clicked(self):
# create text file
file = QtCore.QFile("save.txt")
file.open(QtCore.QIODevice.WriteOnly)
# open data stream
out = QtCore.QDataStream(file)
# recursively write model item into the datastream
self.save_item(self.model.invisibleRootItem(), out)
def save_item(self, item, out):
for i in range(0, item.rowCount()):
child = item.child(i)
child.write(out)
self.save_item(child, out)
def main():
app = QtGui.QApplication(sys.argv)
form = MainForm()
form.show()
app.exec_()
if __name__ == '__main__':
main()
hope this helps, regards
|
Is this the best way to ensure that a python unicode "string" is encoded in utf-8?
Question: Given in arbitrary "string" from a library I do not have control over, I want
to make sure the "string" is a unicode type and encoded in utf-8. I would like
to know if this is the best way to do this:
import types
input = <some value from a lib I dont have control over>
if isinstance(input, types.StringType):
input = input.decode("utf-8")
elif isinstance(input, types.UnicodeType):
input = input.encode("utf-8").decode("utf-8")
In my actual code I wrap this in a try/except and handle the errors but I left
that part out.
Answer: A Unicode object is not encoded (it is internally but this should be
transparent to you as a Python user). The line
`input.encode("utf-8").decode("utf-8")` does not make much sense: you get the
exact same sequence of Unicode characters at the end that you had in the
beginning.
if isinstance(input, str):
input = input.decode('utf-8')
is all you need to ensure that str objects (byte strings) are converted into
Unicode strings.
|
Python socket.accept nonblocking?
Question: Is there a way I can use python's socket.accept() in a non-blocking way that
simply runs it and lets me just check if it got any new connections? I
_really_ don't want to use threading. Thanks.
Answer: You probably want something like `select.select()` (see
[documentation](http://docs.python.org/library/select.html#select.select)).
You supply `select()` with three lists of sockets: sockets you want to monitor
for readability, writability, and error states. The server socket will be
readable when a new client is waiting.
The `select()` function will block until one of the socket states has changed.
You can specify an optional fourth parameter, `timeout`, if you don't want to
block forever.
Here is a dumb echo server example:
import select
import socket
server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
server_socket.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
server_socket.bind(('', 8888))
server_socket.listen(5)
print "Listening on port 8888"
read_list = [server_socket]
while True:
readable, writable, errored = select.select(read_list, [], [])
for s in readable:
if s is server_socket:
client_socket, address = server_socket.accept()
read_list.append(client_socket)
print "Connection from", address
else:
data = s.recv(1024)
if data:
s.send(data)
else:
s.close()
read_list.remove(s)
Python also has `epoll`, `poll`, and `kqueue` implementations for platforms
that support them. They are more efficient versions of `select`.
|
Py2exe lxml woes
Question: I have a wxpython application that depends on lxml and works well when running
it through the python interpreter. However, when creating an exe with py2exe,
I got this error
ImportError: No module named _elementpath
I then used `python setup.py py2exe -p lxml` and I did not get the above error
but another one saying
ImportError: No module named gzip
Could anyone let me know what the problem is and how I can fix it. Also should
I put any dll files like libxml2, libxslt etc in my dist folder? I searched
the computer and did not find these files, so maybe they aren't needed?
Thanks.
Edit: I just tried with `python setup.py py2exe -p -i gzip` and the exe was
created. But the exe generated does not run. I double click it and it doesn't
do anything.
Here's the setup.py script i'm using
from py2exe.build_exe import py2exe
from distutils.core import setup
setup( windows=[{"script": "gui.py"}] )
Edit2: I tried using cx_freeze as an alternative , but got the same
ImportError: No module named _elementpath
error. Didn't know how to proceed after that.
Answer: Py2exe allows you to specify additional packages/modules to include with the
`options` argument to `setup()`, in case they are not automatically detected.
The following should work:
from distutils.core import setup
import py2exe
setup(
windows=[{'script': 'gui.py'}],
options={
'py2exe':
{
'includes': ['lxml.etree', 'lxml._elementpath', 'gzip'],
}
}
)
I've also recently discovered [PyInstaller](http://www.pyinstaller.org/),
which has built-in support for a number of well-known packages, including
lxml, so that might be worth a try as well.
|
Generating cyclic permutations / reduced Latin Squares in Python
Question: Was just wondering what's the most efficient way of generating all the cyclic
permutations of a list in Python. In either direction. For example, given a
list `[1, 2, 3, 4]`, I want to generate either:
[[1, 2, 3, 4],
[4, 1, 2, 3],
[3, 4, 1, 2],
[2, 3, 4, 1]]
where the next permutation is generated by moving the last element to the
front, or:
[[1, 2, 3, 4],
[2, 3, 4, 1],
[3, 4, 1, 2],
[4, 1, 2, 3]]
where the next permutation is generated by moving the first element to the
back.
The second case is slightly more interesting to me because it results in a
reduced Latin square (the first case also gives a Latin square, just not
reduced), which is what I'm trying to use to do experimental block design. It
actually isn't that different from the first case since they're just re-
orderings of each other, but order does still matter.
The current implementation I have for the first case is:
def gen_latin_square(mylist):
tmplist = mylist[:]
latin_square = []
for i in range(len(mylist)):
latin_square.append(tmplist[:])
tmplist = [tmplist.pop()] + tmplist
return latin_square
For the second case its:
def gen_latin_square(mylist):
tmplist = mylist[:]
latin_square = []
for i in range(len(mylist)):
latin_square.append(tmplist[:])
tmplist = tmplist[1:] + [tmplist[0]]
return latin_square
The first case seems like it should be reasonably efficient to me, since it
uses `pop()`, but you can't do that in the second case, so I'd like to hear
ideas about how to do this more efficiently. Maybe there's something in
`itertools` that will help? Or maybe a double-ended queue for the second case?
Answer: You can use collections.deque:
from collections import deque
g = deque([1, 2, 3, 4])
for i in range(len(g)):
print list(g) #or do anything with permutation
g.rotate(1) #for right rotation
#or g.rotate(-1) for left rotation
It prints:
[1, 2, 3, 4]
[4, 1, 2, 3]
[3, 4, 1, 2]
[2, 3, 4, 1]
To change it for left rotation just replace `g.rotate(1)` with `g.rotate(-1)`.
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System.DateTime format as a web service arg
Question: I would like to use a web service which is written on .NET. I should pass a
date value to a method `webservicemethod(on_date)`. It's written in a
description that format of this date is `System.DateTime`. I'm using Python as
a client language. After googling I tried to use many combinations but without
success. This parameter is a string, but what should this string looks like?
from SOAPpy import WSDL
server = WSDL.Proxy('http://www.cbr.ru/DailyInfoWebServ/DailyInfo.asmx?WSDL')
print server.EnumValutes(False) - works !
print server.GetCursOnDate('1/1/2011')
<SOAPpy.Types.structType GetCursOnDateResponse at 57517192>: {}
Answer: .Net uses [ISO
8601](http://en.wikipedia.org/wiki/ISO_8601#Combined_date_and_time_representations)
time format when representing (or parsing) it in string format.
Example: `2007-04-05T14:30`
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Mercurial CGI (hgweb.cgi) fails
Question: I have Mercurial 1.8.1, Python 2.6.6 installed on Win 2k8 R2 running on a vm.
I have tried installing from msi, source and using tortisehg. Command-line Hg
works fine but I get the same error when running the hgweb.cgi:
Traceback (most recent call last):
File ".\hgweb.cgi", line 17, in
application = hgweb(config)
File "mercurial\hgweb\__init__.pyc", line 26, in hgweb
File "mercurial\hgweb\hgwebdir_mod.pyc", line 61, in __init__
File "mercurial\hgweb\hgwebdir_mod.pyc", line 70, in refresh
File "mercurial\ui.pyc", line 35, in __init__
File "mercurial\demandimport.pyc", line 75, in __getattribute__
File "mercurial\demandimport.pyc", line 47, in _load
File "mercurial\util.pyc", line 576, in
File "mercurial\demandimport.pyc", line 85, in _demandimport
File "mercurial\windows.pyc", line 21, in
File "mercurial\demandimport.pyc", line 75, in __getattribute__
File "mercurial\demandimport.pyc", line 47, in _load
File "mercurial\osutil.pyc", line 12, in
File "mercurial\osutil.pyc", line 10, in __load
ImportError: DLL load failed: The specified module could not be found.
The other answers I have found on SO and elsewhere pointed me to try
installing from source, dropping the pure osutil into the install, or
installing an older version. I have tried them all.
This is especially frustrating because I have other, similar non-vm machines
running fine but have been unable to find the disconnect.
Ideas?
Answer: I had the same error using following system configuration
* Python-2.6.6 installed as msi
* mercurial-1.8.2-x86 installed as msi
* IIS7
I solved this problem simply:
1. Python has been installed early
2. Uninstall Mercurial msi package
3. Download and install "Mercurial-1.8.2 (32-bit py2.6)" installer from [mercurial website](http://mercurial.selenic.com/wiki/Download#Windows "here") which is marked as "_This is recommended for hgweb setups_ ".
4. copyed content of C:\Python26\Lib\site-packages\mercurial\ to the directory used in IIS7 website setup.
Till now all is working. Hope this will help.
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Subsets and Splits