case — Advanced Examples

Defines a pattern branch inside a match statement (3.10+)

EasyIntermediateAdvancedExpert

Case exhaustiveness and edge cases

Ensuring all cases are handled.

python
# Simulating exhaustive matching
from enum import Enum

class Color(Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

def describe_color(c):
    match c:
        case Color.RED:
            return "Warm color"
        case Color.GREEN:
            return "Cool color"
        case Color.BLUE:
            return "Cool color"
        # No wildcard - if a new variant is added,
        # this will return None (implicit)

for c in Color:
    print(f"{c.name}: {describe_color(c)}")

# Case with walrus-like capture
data = {"type": "user", "name": "Alice", "age": 30, "role": "admin"}
match data:
    case {"type": "user", "name": str(name), **rest}:
        print(f"User {name}, extra fields: {rest}")
Expected Output
RED: Warm color
GREEN: Cool color
BLUE: Cool color
User Alice, extra fields: {'age': 30, 'role': 'admin'}

Use ** in mapping patterns to capture remaining keys. For exhaustive matching with enums, omit the wildcard so that missing cases return None (or add explicit error handling).

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