Logging and debugging

When a program does the wrong thing, you need two tools: a way to see what it was doing (logging) and a way to stop it and poke around (debugging). Python gives you a surprisingly capable version of each in the standard library — logging for structured, level-aware observability, and pdb for interactive stepping. This guide covers both, and the judgement calls for when to reach for which.

Start here

If logging or pdb is new to you, work through the Learn section in order — four short notebooks, around fifteen minutes each. Every code cell can be edited and run in place, directly on the page; no install required.

If you already know the basics and are looking for a specific technique, jump to the Recipes section, or scan the Reference for logging methods and pdb commands.

What this guide covers

Learn — your first log message, log levels and formatting, logging to files, debugging with pdb.

Recipes — project-wide logging configuration, custom handlers, effective breakpoints, common mistakes to avoid.

Reference — logging module API, log-format directives, pdb command list.

Concepts — understanding log levels, and why logging beats print for anything beyond a scratch script.