Question

Short version (if you can answer the short version it does the job for me, the rest is mainly for the benefit of other people with a similar task):

In python in Windows, I want to create 2 file objects, attached to the same file (it doesn’t have to be an actual file on the hard-drive), one for reading and one for writing, such that if the reading end tries to read it will never get EOF (it will just block until something is written). I think in linux os.mkfifo() would do the job, but in Windows it doesn’t exist. What can be done? (I must use file-objects).

Some extra details:
I have a python module (not written by me) that plays a certain game through stdin and stdout (using raw_input() and print). I also have a Windows executable playing the same game, through stdin and stdout as well. I want to make them play one against the other, and log all their communication.

Here’s the code I can write (the get_fifo() function is not implemented, because that’s what I don’t know to do it Windows):

class Pusher(Thread):
        def __init__(self, source, dest, p1, name):
                Thread.__init__(self)
                self.source = source
                self.dest = dest
                self.name = name
                self.p1 = p1

        def run(self):
                while (self.p1.poll()==None) and\
                      (not self.source.closed) and (not self.source.closed):
                        line = self.source.readline()
                        logging.info('%s: %s' % (self.name, line[:-1]))
                        self.dest.write(line)
                        self.dest.flush()


exe_to_pythonmodule_reader, exe_to_pythonmodule_writer =\
                          get_fifo()
pythonmodule_to_exe_reader, pythonmodule_to_exe_writer =\
                          get_fifo()

p1 = subprocess.Popen(exe, shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE)

old_stdin = sys.stdin
old_stdout = sys.stdout

sys.stdin = exe_to_pythonmodule_reader
sys.stdout = pythonmodule_to_exe_writer

push1 = Pusher(p1.stdout, exe_to_pythonmodule_writer, p1, '1')
push2 = Pusher(pythonmodule_to_exe_reader, p1.stdin, p1, '2')

push1.start()
push2.start()
ret = pythonmodule.play()
sys.stdin = old_stdin
sys.stdout = old_stdout

Answer 1

Following the two answers above, I accidentally bumped into the answer. os.pipe() does the job. Thank you for your answers.

I’m posting the complete code in case someone else is looking for this:

import subprocess
from threading import Thread
import time
import sys
import logging
import tempfile
import os

import game_playing_module

class Pusher(Thread):
    def __init__(self, source, dest, proc, name):
        Thread.__init__(self)
        self.source = source
        self.dest = dest
        self.name = name
        self.proc = proc

    def run(self):
        while (self.proc.poll()==None) and\
              (not self.source.closed) and (not self.dest.closed):
            line = self.source.readline()
            logging.info('%s: %s' % (self.name, line[:-1]))
            self.dest.write(line)
            self.dest.flush()

def get_reader_writer():
    fd_read, fd_write = os.pipe()
    return os.fdopen(fd_read, 'r'), os.fdopen(fd_write, 'w')

def connect(exe):
    logging.basicConfig(level=logging.DEBUG,\
                        format='%(message)s',\
                        filename=LOG_FILE_NAME,
                        filemode='w')

    program_to_grader_reader, program_to_grader_writer =\
                              get_reader_writer()

    grader_to_program_reader, grader_to_program_writer =\
                              get_reader_writer()

    p1 = subprocess.Popen(exe, shell=False, stdin=subprocess.PIPE, stdout=subprocess.PIPE)        

    old_stdin = sys.stdin
    old_stdout = sys.stdout

    sys.stdin = program_to_grader_reader
    sys.stdout = grader_to_program_writer

    push1 = Pusher(p1.stdout, program_to_grader_writer, p1, '1')
    push2 = Pusher(grader_to_program_reader, p1.stdin, p1, '2')

    push1.start()
    push2.start()

    game_playing_module.play()

    sys.stdin = old_stdin
    sys.stdout = old_stdout

    fil = file(LOG_FILE, 'r')
    data = fil.read()
    fil.close()
    return data

if __name__=='__main__':
    if len(sys.argv) != 2:
        print 'Usage: connect.py exe'
        print sys.argv
        exit()
    print sys.argv
    print connect(sys.argv[1])