thread hangs when using subprocess only in specific circumstances

[Toon Verstraelen]

Hi,

I recently had a thread problem and I could reduce it to a very short
example that shows the problem. I hope it has its origin in my
misunderstanding of how python threads work. Here it is:

--- my_thread.py ---

import threading
from subprocess import Popen, PIPE, STDOUT

class MyThread(threading.Thread):
    def run(self):
        print "before Popen"
        sp = Popen(["ls", "-al"], stdout=PIPE, stderr=STDOUT)
        print "before first line"
        for line in sp.stdout:
            print line[:-1]
        print "after last line"


t = MyThread()
t.start()

--- main.py ---

import my_thread


----------------

If I start my_thread.py directly there is no problem, but when i run
'python main.py' the thread hangs on the creation of the Popen object. I'm
using python 2.4.2 on gentoo linux. Can someone reproduce the problem?

Thanks for reading this.

Toon