Testcase of Python issue 706263, with a workaround.

4096_tc.py

#This file is a testcase of http://bugs.python.org/issue706263 with a workaround.
#Z:\>python 4096_tc.py
#Z:\>cat result.txt
#stdin: 0 stdout: 1 stderr: 2
#Bytes printed: 199998
#Z:\>pythonw 4096_tc.py
#Z:\>cat result.txt
#stdin: -2 stdout: -2 stderr: -2
#Bytes printed before exception was raised: 4096
#Traceback (most recent call last):
#  File "4096_tc.py", line 42, in <module>
#    sys.stdout.write('a ')
#IOError: [Errno 9] Bad file descriptor

def fixup_win_gui_stdio():
    """Correct potential issues with a win32 gui application that uses stdio.
    
    A Win32 GUI Application sets it's stdin, stdout, and stderr to -2 or -1 to indicate that the streams do not exist.
    With default configurations, writes to stdout/err will raise InvalidHandle after 4096 bytes (the default buffer size).
    
    See http://bugs.python.org/issue706263 for more information.
    """
    import sys, os
    if hasattr(sys.stdin, 'fileno') and sys.stdin.fileno() < 0:
        sys.stdin = open(os.devnull, "rb")
    if hasattr(sys.stdout, 'fileno') and sys.stdout.fileno() < 0:
        sys.stdout = open(os.devnull, "wb")
    if hasattr(sys.stderr, 'fileno') and sys.stderr.fileno() < 0:
        sys.stderr = open(os.devnull, "wb")

#Uncomment to test above solution
#fixup_win_gui_stdio()

import sys
import traceback
counter = 0

fout = open('result.txt', 'w')

try:
    for counter in range(100000):
        sys.stdout.write('a ')
        #sys.stdout.flush()
    fout.write('stdin: %s stdout: %s stderr: %s\n'%(sys.stdin.fileno(), sys.stdout.fileno(), sys.stderr.fileno()))
    fout.write('Bytes printed: %d\n' % (counter*2))
except:
    fout.write('stdin: %s stdout: %s stderr: %s\n'%(sys.stdin.fileno(), sys.stdout.fileno(), sys.stderr.fileno()))
    fout.write('Bytes printed before exception was raised: %d\n' % (counter*2))
    traceback.print_exc(100, fout)
finally:
    fout.close()