parsing a file [newbie]

[Alex Martelli]

"Langa Kentane" <LangaK at discoveryhealth.co.za> wrote in message
news:mailman.979720698.24494.python-list at python.org...
> How do I read a file.

You open it for reading, then apply to the resulting Python fileobject
its methods read (to get all bytes, or up to N bytes), readline (to get
one line at a time) or readlines (to get all lines, or lines accounting
for up to N bytes).


> This is what I want to do.
> Run a command using os.popen and store the file info that it returns to x

So far, so pretty easy:

    x = os.popen(thecommand, "r")

> Open file x and read the contents.[ contents of x will be a mount output.]

x is already open.  You can read it with readline, read, readlines, ...


> Go to the third column of the mount output and and store in y

Presumably you want the third column _of each line_, right?  Simplest
way (avoiding the intermediate variable 'x') would be one statement:

y = [line.split()[2] for line in os.popen(thecommand, "r").readlines()]


If you insist on using x, you'll need two statements:

x = os.popen(thecommand, "r")
y = [line.split()[2] for line in x.readlines()]


Alex