How to debug python CLI that takes stdin?

Question

I\'m trying to debug a Python CLI I wrote that can take its arguments from stdin. A simple test case would have the output of

echo \"test\" | python mytool.p         


        

Answer 1

You can use another file descriptor. With bash you can create a new file descriptor with:

exec 3<> test.txt

And then on your python file have something like:

#!/usr/bin/python

# Use fd 3 as another stdin file.
import os
stdin=os.fdopen(3)

while True:
    s=stdin.readline()
    import pdb; pdb.set_trace()
    print len(s)

Just runing your script will use that test.txt as input, and you can use stdin on stdin. It can be used as well with pipes if you need.