WHAT is [0] in subprocess.Popen(blah).communicate()[0]

[Fredrik Lundh]

johnny wrote:

> Can someone tell me what is the reason "[0]" appears after
> ".communicate()"
> 
> For example:
> last_line=subprocess.Popen([r"tail","-n 1", "x.txt"],
> stdout=subprocess.PIPE).communicate()[0]

as explained in the documentation, communication() returns two values, 
as a tuple.  [0] is used to pick only the first one.

see the Python tutorial for more on indexing and slicing.

</F>