python behaviour when passed an asterisk

Question

I'm writing a small script, that should be able to handle multiple files. So I've added that files can be passed comma seperated, and do a arg.split(',') and then handle each one.

Now I've wanted to add asterisk as input possibility like

python myPythonScript.py -i folder/*

If I print the the argument to option -i right when I access it the first time I get

folder/firstFileInFolder.txt

But if I call my script with

python myPythonScript.py -i someFolder/someFile,folder/*

it works just fine. Does anyone have an idea, why python might behave that way?

Answer 1

Try to run this script

import sys

for arg in sys.argv:
    print arg

python script.py *

your shell expands the asterisk before python sees it.

Answer 2

As mentioned in the comments, your shell is expanding the asterisk for the non-comma separated case. If you know that the user may specify an asterisk as part of a file name as in your second example, you can have Python do the path expansion by using the glob module.

from glob import glob
glob('*')

code which would allow either the shell or Python to do asterisk expansion may look something like this:

import glob
file_list = []
for pattern in sys.argv[1:]:
    file_list.extend(glob.glob(pattern))

In your case, using a comma as a separator would then prevent you from using a comma as part of a filename.