debugging a python script taking input from sys.stdin in pycharm

Question

I want to debug a small python script that takes input from stdin and sends it to stdout. Used like this:

filter.py < in.txt > out.txt

There does not seem to be a way to configure Pycharm debugging to pipe input from my test data file.

This question has been asked before, and the answer has been, basically "you can't--rewrite the script to read from a file."

I modified the code to take a file, more or less doubling the code size, with this:

import argparse

if __name__ == '__main__':
    cmd_parser = argparse.ArgumentParser()
    cmd_parser.add_argument('path', nargs='?', default='/dev/stdin')
    args = cmd_parser.parse_args()
    with open(in_path) as f:
        filter(f)

where filter() now takes a file object open for write as a parameter. This permits backward compatibility so it can be used as above, while I am also able to invoke it under the debugger with input from a file.

I consider this an ugly solution. Is there a cleaner alternative? Perhaps something that leaves the ugliness in a separate file?

Jack · Accepted Answer · 2017-06-29 15:59:42Z

1

If you want something simpler, you can forgo argparse entirely and just use the sys.argv list to get the first argument.

import sys

if len(sys.argv) > 1:
    filename = sys.argv[1]
else:
    filename = sys.stdin

with open(filename) as f:
    filter(f)

answered Jun 29, 2017 at 15:59

Jack

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2 Comments

mohawkTrail Over a year ago

I assume the preceding would need the if __name__ == '__main__': bit when merged with the def filter(file): definition (filter() def not shown in my example either).

Jack Over a year ago

Yes, you can nest the above code under the if __name__ == '__main__' block so that it only runs when called as a script and not when imported as a module.

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