Python: Passing value of a string variable as argument in Popen

Question

What is the proper way to pass values of string variables to Popen function in Python? I tried the below piece of code

var1 = 'hello'
var2 = 'universe'
p=Popen('/usr/bin/python /apps/sample.py ' + '"' + str(eval('var1')) + ' ' + '"' + str(eval('var2')), shell=True)

and in sample.py, below is the code

print sys.argv[1]
print '\n'
print sys.argv[2]

but it prints the below output

hello universe
none

so its considering both var1 and var2 as one argument. Is this the right approach of passing values of string variables as arguments?

str(eval('var1'))is the same as 'var1'.

Matthias
– Matthias

2013-10-21 08:27:55 +00:00
Commented Oct 21, 2013 at 8:27 — Matthias
– Matthias, Commented Oct 21, 2013 at 8:27

warvariuc · Accepted Answer · 2013-10-21 08:22:27Z

1

This should work:

p = Popen('/usr/bin/python /apps/sample.py {} {}'.format(var1, var2), shell=True)

Learn about string formatting .

Second, passing arguments to scripts has its quirks: http://docs.python.org/2/library/subprocess.html#subprocess.Popen

This works for me:

test.py:

#!/usr/bin/env python

import sys

print sys.argv[1]
print '\n'
print sys.argv[2]

Then:

chmod +x test.py

Then:

Python 2.7.4 (default, Jul  5 2013, 08:21:57) 
>>> from subprocess import Popen
>>> p = Popen('./test.py {} {}'.format('hello', 'universe'), shell=True)
>>> hello


universe

edited Oct 21, 2013 at 8:22

answered Oct 21, 2013 at 8:10

warvariuc

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2 Comments

Iowa Over a year ago

and is there a way to return control from the called python script to the calling python script?

warvariuc Over a year ago

The control is returned to the called script when it terminates.

Nilesh · Accepted Answer · 2013-10-21 11:05:09Z

0

var1 = 'hello'
var2 = 'universe'
p=Popen("/usr/bin/python /apps/sample.py %s %s"%(str(eval('var1')), str(eval('var2'))), shell=True)

Passing format specifier is nice way to do it.

answered Oct 21, 2013 at 11:05

Nilesh

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