Pipe Error on Windows?

Chris S. chrisks at NOSPAM.udel.edu
Tue Sep 7 02:30:15 CEST 2004


When I use os.popen3 to communicate through pipes under Windows, the 
data is only one-way, namely from child to parent. Below are example 
scripts. Is this a bug in the Windows implementation or am I missing 
something?
Any help is appreciated.

#----------------------------------
# controller.py
import threading
import sys
import time
import os

(w,r,e) = os.popen3('engine.py')

def receive(r):
     print 'staring recv'
     while 1:
         # get data
         try:
             data = r.readline()
         except Exception, e:
             print e
             break
         if not len(data):
             time.sleep(0.1)
             continue
         else:
             print 'controller received:', data
     print 'stopping recv'

t = threading.Thread(target=receive, args=(r,))
t.setDaemon(True)
t.start()

for i in range(5):
     time.sleep(1)
     if not w.closed:
         print >>w, 'controller '+str(i)
         w.flush()

print 'final:', ''.join(r.readlines())
print 'errors:', ''.join(e.readlines())

r.close()
w.close()
e.close()

#-------------------------
# engine.py
import sys
import threading
import time

outfile = open('enginetest.data', 'w')

def receive():
     global outfile
     print >>outfile, 'starting recv'
     while 1:
         # get data
         try:
             data = sys.stdin.readline()
         except Exception, e:
             print >>outfile, 'error:', e
             break
         if not len(data):
             time.sleep(0.1)
             continue
         else:
             print >>outfile, data
         print >>outfile, data
     print >>outfile, 'stopping recv'

t = threading.Thread(target=receive)
t.setDaemon(True)
t.start()

for i in range(4):
     time.sleep(1)
     if not sys.stdout.closed:
         print >>sys.stdout, 'engine',str(i)
         sys.stdout.flush()

outfile.close()



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