Control Flow: Structural Pattern Matching (match-case in Python 3.10+)

1Concept

Python 3.10 introduced structural pattern matching via match-case, supporting literal matching, sequence unpacking, mapping patterns, and guarded case conditions.

2Architecture Diagram

match command.split():
    case ["quit"]: ...
    case ["load", filename]: ...
    case ["move", x, y] if int(x) > 0: ...

3Code Example

def route_action(event: dict):
    match event:
        case {"type": "CLICK", "x": x, "y": y} if x > 0 and y > 0:
            return f"Valid Click at coordinates ({x}, {y})"
        case {"type": "KEYPRESS", "key": ("ENTER" | "RETURN")}:
            return "Form submitted via Enter key"
        case {"type": "LOGOUT"}:
            return "User logged out"
        case _:
            return "Unhandled event"

print(route_action({"type": "CLICK", "x": 120, "y": 450}))
print(route_action({"type": "KEYPRESS", "key": "ENTER"}))
print(route_action({"type": "SCROLL"}))

4Expected Output

Valid Click at coordinates (120, 450)
Form submitted via Enter key
Unhandled event

5Key Takeaways

• ✓match-case unpacks nested dictionaries and lists natively without manual indexing.
• ✓Guard clauses (case ... if condition) add powerful validation filters.
• ✓case _ serves as the catch-all wildcard.