A commentator on my entry on why your main program should be import able mentioned that a third reason is to beable to unit test your program. I agree with the sentiment in general,but in specific I've never been able to get unit testing of my mainprogram code to work very well.

While I can unit test most of the low-level code involved in a program,I've found that much of the high level code, the stuff that goes in themain program, has two

The CPython interpreter doesn't run Python code directly, but first compiles it to bytecode . Because this parsingand compiling steps are somewhat time-consuming, CPython optimizesthings by saving the compiled bytecodes into .pyc files (or .pyo files if you used the -O switch to python ), and trying to usethem when possible.This speed increase doesn't necessarily matter all that much for aprogram that runs a long time, but it does matter for typical utilityprograms, which only run for a