Parsing a stdout in Python

Question

In Python I need to get the version of an external binary I need to call in my script.

Let's say that I want to use Wget in Python and I want to know its version.

I will call

os.system( "wget --version | grep Wget" ) 

and then I will parse the outputted string.

How to redirect the stdout of the os.command in a string in Python?

Answer 1

use subprocess.

Answer 2

Use subprocess instead.

Answer 3

One "old" way is:

fin,fout=os.popen4("wget --version | grep Wget")
print fout.read()

The other modern way is to use a subprocess module:

import subprocess
cmd = subprocess.Popen('wget --version', shell=True, stdout=subprocess.PIPE)
for line in cmd.stdout:
    if "Wget" in line:
        print line

Answer 4

Use the subprocess module:

from subprocess import Popen, PIPE
p1 = Popen(["wget", "--version"], stdout=PIPE)
p2 = Popen(["grep", "Wget"], stdin=p1.stdout, stdout=PIPE)
output = p2.communicate()[0]

Answer 5

If you are on *nix, I would recommend you to use commands module.

import commands

status, res = commands.getstatusoutput("wget --version | grep Wget")

print status # Should be zero in case of of success, otherwise would have an error code
print res # Contains stdout