Shell script or Python?

Every now and then a discussion arises on whether some piece of scripting functionality should be written as a basic shell script or in Python. Here is a handy step-by-step guide to answering the question. Start at the beginning and work your way down until you have your answer.

Will the script be longer than one screenful of text (80 lines)? If yes ⇒ Python.

Will the script ever need to be run on a non-unix platform such as Windows (including Cygwin)? If yes ⇒ Python.

Does the script require command line arguments? If yes ⇒ Python.

Will the script do any networking (e.g. call curl or wget)? If yes ⇒ Python.

Will the script use any functionality that is in Python standard library but is not available as a preinstalled binary absolutely everywhere (e.g. compressing with 7zip)? If yes ⇒ Python.

Will the script use any control flow (functions/while/if/etc)? If yes ⇒ Python.

Will the script have modifications in the future rather than being written once and then dropped? If yes ⇒ Python.

Will the script be edited by more than one person? If yes ⇒ Python.

Does the script call into any non-trivial Unix helper tool (awk, sed, etc)? If yes ⇒ Python.

Does the script call into any tool whose behaviour is different on different platforms (e.g. mkdir -p, some builtin shell functionality)? If yes ⇒ Python.

Does the script need to do anything in parallel? If yes ⇒ Python.

If none of the above match then you have a script that proceeds in a straight line calling standard and simple Unix commands and never needs to run on a non-unix platform. In this case a shell script might be ok. But you might still consider doing it in Python, because scripts have a tendency to become more and more complex with time.