Python is fantastic for little (or large!) bits of logic, but its handling of input is clunky enough to put me off for tiny things. AFAIK the boilerplate you need to get to working on the fields on each line is:

  import sys
  for line in sys.stdin:
    fields = line.split()
    # now you can do your logic

If you want to use regular expressions, that's another import.

Python also doesn't play well with others in a pipeline. You can use python -c, but you can't use newlines inside the argument (AFAICT), so you're very limited in what you can do.