Propagate system call interruptions in threads
Question: I'm running two python threads (`import threading`). Both of them are blocked
on a `open()` call; in fact they try to open named pipes in order to write in
them, so it's a normal behaviour to block until somebody try to read from the
named pipe.

In short, it looks like:

    
    
    import threading
    
    def f():
        open('pipe2', 'r')
    
    if __name__ == '__main__':
        t = threading.Thread(target=f)
        t.start()
        open('pipe1', 'r')
    

When I type a ^C, the `open()` in the main thread is interrupted (raises
`IOError` with errno == 4).

My problem is: the `t` threads still waits, and I'd like to propagate the
interruption behaviour, in order to make it raise `IOError` too.


Answer: I found this in python docs:  
" ... only the main thread can set a new signal handler, and the main thread
will be the only one to receive signals (this is enforced by the Python signal
module, even if the underlying thread implementation supports sending signals
to individual threads). This means that signals can’t be used as a means of
inter-thread communication. Use locks instead. "  
Maybe you should also check these docs:  
[exceptions.KeyboardInterrupt](http://docs.python.org/release/2.6.7/library/exceptions.html#exceptions.KeyboardInterrupt)

[library/signal.html](http://docs.python.org/release/2.6.7/library/signal.html)

One other idea is to use select to read the pipe asynchronously in the
threads. This works in Linux, not sure about Windows (it's not the cleanest,
nor the best implementation):

    
    
       #!/usr/bin/python
    
       import threading
       import os
       import select
    
       def f():
               f = os.fdopen(os.open('pipe2', os.O_RDONLY|os.O_NONBLOCK))
               finput = [ f ]
               foutput = []
               # here the pipe is scanned and whatever gets in will be printed out
               # ...as long as 'getout' is False
               while finput and not getout:
                       fread, fwrite, fexcep = select.select(finput, foutput, finput)
                       for q in fread:
                               if q in finput:
                                       s = q.read()
                                       if len(s) > 0:
                                               print s
    
       if __name__ == '__main__':
               getout = False
               t = threading.Thread(target=f)
               t.start()
               try:
                       open('pipe1', 'r')
               except:
                       getout = True
    

