python and string from list as parameter

Question

I'm trying to write a Python script that reads lines of strings from a file and executes a bash-shell command with each line as parameter:

#!/usr/bin/env python
# -*- coding: utf-8 -*-
import os

lines = [line.strip() for line in open('/tmp/i586rpm.txt')]
for rpm in lines:
    try:
        s = os.system("rpm -qip") % lines

    except Exception:
        print "Something wrong"

But I always get an error. I think that there is something wrong with % lines.

Any ideas?

unwind · Accepted Answer · 2012-01-16 12:21:20Z

6

Yes, you're not building the command string properly. Try:

s = os.system("rpm -qip \"%s\"" % rpm)

answered Jan 16, 2012 at 12:21

unwind

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Comments

jcollado · Accepted Answer · 2012-01-16 12:23:46Z

4

There are a few things that could be improved:

Uses os.system instead of subprocess.Popen (for more information, please have look at the documentation)
Iterates over lines, but it doesn't use the iteration variable (rpm)
Attemps to format the output string from os.system with lines as a parameter.

My advice is to use this code:

for line in lines:
    p = subprocess.Popen('rpm -qip {0}'.format(line),
                         shell=True,
                         stdout=subprocess.PIPE)
    stdout, stderr = p.communicate()

answered Jan 16, 2012 at 12:23

jcollado

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4 Comments

glglgl Over a year ago

This answer is by far better than unwind's.

Alexander Over a year ago

Great.But how i can output rpm -qip {0} into directly into shell or file?

jcollado Over a year ago

@user413036 I'm not sure what do you mean. If the problem is regarding {0}, note that '{0}'.format(line) is equivalent to '%s' % line.

glglgl Over a year ago

@user413036 You probably don't want to output it into a shell, you just wand to execute it. And that's what the call above for. Maybe even better p = subprocess.Popen(['rpm', '-qip', '{0}'.format(line)], stdout=subprocess.PIPE) - the shell is not needed here.

bpgergo · Accepted Answer · 2012-01-16 12:37:14Z

-1

instead of

for rpm in lines:
    s = os.system("rpm -qip") % lines

do this

for rpm in lines:
    s = os.system('rpm -qip "%s"' % rpm)

EDIT correct the code

edited Jan 16, 2012 at 12:37

answered Jan 16, 2012 at 12:21

bpgergo

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1 Comment

TyrantWave Over a year ago

That still won't work as you put the % rpm outside of the os.system call. s = os.system('rpm -qip "%s"' % rpm)

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