Python Pattern Matching with match Expressions
The match expression compares a value against a series of patterns and executes code based on which pattern matches. match is exhaustive: the compiler forces you to handle every possible value, eliminating unhandled state bugs.
"A match expression is like a biometric sorting machine: coins roll down chutes with precision-cut slots. Every single coin denomination has an exact matching slot, with a catch-all tray (_) at the bottom for foreign coins."
Deep Dive: How It Works
Exhaustiveness: You must cover all possible cases (or provide a catch-all _ arm).
Match Arms: pattern => expression, separated by commas.
Match Guards: pattern if condition => expr adds extra boolean constraints.
Syntax Blueprint
match code { 200 => "OK", 404 => "Not Found", _ => "Unknown" }Evaluates top-to-bottom and returns the resulting expression of the first matching arm.
Core Rules to Remember
Common Beginner Traps & How to Fix Them
Non-exhaustive match on integers or enums.Why it happens: Matching integers 1, 2 without a wildcard _ causes E0004: non-exhaustive patterns.
How to fix: Always include the wildcard pattern _ => ... for unbounded types.
Live Interactive Example
Hit Run Code to see it liveYour Turn: Micro Challenge
No pressure! Edit the starter code below and test your solution with instant feedback.
Match dice roll outcome
- Given let roll = 6;
- Use match roll { 6 => "Critical Hit", 1 => "Critical Miss", _ => "Normal Roll" };
- Print "Outcome: Critical Hit".
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