case — Intermediate Examples

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

EasyIntermediateAdvancedExpert

Case with capture and type patterns

Extracting values and checking types in case clauses.

python
# Type patterns with capture
def process(value):
    match value:
        case int(n):
            print(f"Integer: {n}")
        case str(s):
            print(f"String: {s!r}")
        case list() as items:
            print(f"List with {len(items)} items")
        case dict() as d:
            print(f"Dict with keys: {list(d.keys())}")
        case None:
            print("None value")
        case _:
            print(f"Other: {type(value).__name__}")

for v in [42, "hello", [1, 2], {"a": 1}, None, 3.14]:
    process(v)

# Starred patterns
match [1, 2, 3, 4, 5]:
    case [first, *rest]:
        print(f"First: {first}, rest: {rest}")

match [1]:
    case [x, *rest] if not rest:
        print(f"Single element: {x}")

case patterns can check types and capture values simultaneously. Use * patterns for variable-length sequences.

Nested case patterns

Pattern matching on complex nested data.

python
# Command parser
commands = [
    {"cmd": "move", "args": {"direction": "north", "speed": 5}},
    {"cmd": "attack", "args": {"target": "dragon"}},
    {"cmd": "heal", "args": {}},
    {"cmd": "unknown"},
]

for command in commands:
    match command:
        case {"cmd": "move", "args": {"direction": d, "speed": int(s)}}:
            print(f"Move {d} at speed {s}")
        case {"cmd": "attack", "args": {"target": str(t)}}:
            print(f"Attack {t}")
        case {"cmd": str(c), "args": dict() as args} if not args:
            print(f"Command {c} with no args")
        case {"cmd": str(c)}:
            print(f"Command {c} (no args key)")
Expected Output
Move north at speed 5
Attack dragon
Command heal with no args
Command unknown (no args key)

case patterns can destructure deeply nested dicts and lists. Guards add extra conditions beyond structural matching.

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