# Fibonacci numbers module
from __future__ import print_function
def fib(n):    # write Fibonacci series up to n
    a, b = 0, 1
    while b < n:
        print(b,)
        a, b = b, a+b

def fib2(n):   # return Fibonacci series up to n
    result = []
    a, b = 0, 1
    while b < n:
        result.append(b)
        a, b = b, a+b
    return result


"""
Explanation: Module 6 - Modules
Scripts and Programs
If you quit from the Python interpreter and enter it again, the definitions you have made (functions and variables) are lost. 
Therefore, if you want to write a somewhat longer program, you are better off using a text editor to prepare the input for the interpreter and running it with that file as input instead. 
This is known as creating a script. 
As your program gets longer, you may want to split it into several files for easier maintenance. 
You may also want to use a handy function that you’ve written in several programs without copying its definition into each program.
Modules
To support this, Python has a way to put definitions in a file and use them in a script or in an interactive instance of the interpreter. 
Such a file is called a module; definitions from a module can be imported into other modules or into the main module (the collection of variables that you have access to in a script executed at the top level and in calculator mode).
A module is a file containing Python definitions and statements. 
The file name is the module name with the suffix .py appended. Within a module, the module’s name (as a string) is available as the value of the global variable __name__.
fib.py
For instance, use your favorite text editor to create a file called fibo.py in the current directory with the following contents:
End of explanation
"""


import fibo

"""
Explanation: Now enter the Python interpreter and import this module with the following command:
End of explanation
"""


fibo.fib(1000)

fibo.fib2(100)

fibo.__name__

"""
Explanation: This does not enter the names of the functions defined in fibo directly in the current symbol table; it only enters the module name fibo there. 
Using the module name you can access the functions:
End of explanation
"""


fib = fibo.fib
fib(500)

"""
Explanation: If you intend to use a function often you can assign it to a local name:
End of explanation
"""


from fibo import fib, fib2
fib(500)

"""
Explanation: More on Modules
A module can contain executable statements as well as function definitions. 
These statements are intended to initialize the module. 
They are executed only the first time the module name is encountered in an import statement.
Each module has its own private symbol table, which is used as the global symbol table by all functions defined in the module. 
Thus, the author of a module can use global variables in the module without worrying about accidental clashes with a user’s global variables. 
On the other hand, if you know what you are doing you can touch a module’s global variables with the same notation used to refer to its functions, modname.itemname.
Modules can import other modules.
It is customary but not required to place all import statements at the beginning of a module (or script, for that matter). The imported module names are placed in the importing module’s global symbol table.
There is a variant of the import statement that imports names from a module directly into the importing module’s symbol table. For example:
End of explanation
"""


from fibo import *
fib(500)

"""
Explanation: This does not introduce the module name from which the imports are taken in the local symbol table (so in the example, fibo is not defined).
import *
There is even a variant to import all names that a module defines:
End of explanation
"""


import fibo, sys
print(dir(fibo))

print(dir(sys))

"""
Explanation: This imports all names except those beginning with an underscore (_).
Note that in general the practice of importing * from a module or package is frowned upon, since it often causes poorly readable code. 
However, it is okay to use it to save typing in interactive sessions.
The dir() Function
The built-in function dir() is used to find out which names a module defines. It returns a sorted list of strings:
End of explanation
"""


a = [1, 2, 3, 4, 5]
import fibo
fib = fibo.fib
print(dir())

"""
Explanation: Without arguments, dir() lists the names you have defined currently:
End of explanation
"""


import builtins
print(dir(__builtin__))

"""
Explanation: Note that it lists all types of names: variables, modules, functions, etc.
dir() does not list the names of built-in functions and variables. If you want a list of those, they are defined in the standard module builtins:
End of explanation
"""


