subprocess: returncode v. poll()

[7stud]

On Sep 20, 1:25 pm, 7stud <bbxx789_0... at yahoo.com> wrote:
> On Sep 20, 1:17 pm, 7stud <bbxx789_0... at yahoo.com> wrote:
>
>
>
> > Hi,
>
> > What is the difference between:
>
> > 1) getting the returncode directly from the subprocess object
> > 2) calling poll() on the subprocess object?
>
> > Here is an example:
>
> > import subprocess
>
> > p = subprocess.Popen("ls", stdout=subprocess.PIPE)
> > print p.returncode
> > print p.poll()
> > print
>
> > print p.stdout.read()[:5]
> > print
>
> > print p.returncode
> > print p.poll()
> > print p.returncode
>
> > --output:--
> > None
> > None
>
> > 10tes
>
> > None
> > 0
> > 0
>
> Hmm....after a little more testing, I don't think returncode
> dynamically updates:
>
> import subprocess
> import time
>
> p = subprocess.Popen("ls", stdout=subprocess.PIPE)
>
> print p.returncode
> time.sleep(5)
> print p.returncode
> time.sleep(2)
> print p.returncode
>
> print p.stdout.read()[:5]
> print p.returncode
>
> --output:--
> None
> None
> None
> 10tes
> None

...but then when is p.returncode set?  And what good is it?