troubles when using a bash command inside a python script

Question

I am trying this on python:

import os

process="find . -type f -name *.out*.xyz'"
print "the number of xyz files is %s" %os.system(process)

When i try it from command line it works, but from python it returns the number 0, when it is 4. I think there must be a problem with the use of os.system. Any help?

Also check out the `subprocess` module. It's prefered over `os.system` these days. — orangeInk, Aug 04 '17 at 10:23
And by "these days", we mean "since its release nearly 13 years ago". — chepner, Aug 04 '17 at 11:46

score 2 · Accepted Answer · answered Aug 04 '17 at 09:54

Yes what you are getting is the return code "0" meaning "successfully completed, no errors" and not the stdout text output "4".

You should look here to get the output: Assign output of os.system to a variable and prevent it from being displayed on the screen

And here to learn about POSIX exit codes: https://en.wikipedia.org/wiki/Exit_status

score 0 · Answer 2 · answered Aug 18 '17 at 15:09

Actually, if you really just need the number of files in Python, try this:

import pathlib
p = pathlib.Path('.')
files = [x for x in p.iterdir() if x.is_file() and x.match('*.csv')]
print("Number of files: {0}".format(len(files)))

Easier, Pythonic and you do not need to fork a sub-process.

troubles when using a bash command inside a python script

2 Answers2