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From: "Joseph L. Casale" <jcasale@activenetwerx.com>
To: "python-list@python.org" <python-list@python.org>
Subject: RE: Running a command line program and reading the result as it runs
Thread-Topic: Running a command line program and reading the result as it runs
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Date: Fri, 23 Aug 2013 10:50:18 +0000
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Xref: csiph.com comp.lang.python:52877

> >> I'm using Python 2.7 under Windows and am trying to run a command line
> >> program and process the programs output as it is running. A number of
> >> web searches have indicated that the following code would work.
> >>
> >> import subprocess
> >>
> >> p =3D subprocess.Popen("D:\Python\Python27\Scripts\pip.exe list -o",
> >>                      stdout=3Dsubprocess.PIPE,
> >>                      stderr=3Dsubprocess.STDOUT,
> >>                      bufsize=3D1,
> >>                      universal_newlines=3DTrue,
> >>                      shell=3DFalse)
> >> for line in p.stdout:
> >>     print line
> >>
> >> When I use this code I can see that the Popen works, any code between
> >> the Popen and the for will run straight away, but as soon as it gets t=
o
> >> the for and tries to read p.stdout the code blocks until the command
> >> line program completes, then all of the lines are returned.
> >>
> >> Does anyone know how to get the results of the program without it
> >> blocking?

Try this:

p =3D subprocess.Popen(args, stdout=3Dsubprocess.PIPE)
for line in p.stdout:
    print(line)
p.wait()

jlc