Error handling

Things go wrong. Files don't exist, networks drop, users type nonsense. Python's exception system is how your program responds to those moments — by recovering cleanly, by failing loudly, or by passing the problem up to someone who can do something about it. This guide takes you from your first try/except to writing your own exception types, and to the trickier question of when not to catch.

Start here

If exceptions are 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 syntax and the built-in exception hierarchy.

What this guide covers

Learn — your first exception, exception types, raising exceptions, cleanup with finally.

Recipes — handling multiple exceptions, custom exceptions, context managers, common mistakes to avoid.

Reference — try/except syntax, built-in exceptions, the exception hierarchy.

Concepts — why error handling matters, how exceptions propagate through the call stack.