taptempo.py is as described: a simple terminal utility to measure out the tempo of repeated keypresses. Start the program, tap a key to the beat of a song, and it will tell you the approximate BPM and the average time between each keypress.

Alas, not even this script is safe from rewrite it in Rust. The Rust version is better, though, because it includes more information in its output, colors, and more documentation.