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