How to use match-case in Python (hint: not for if statements)

Source: Dev.to

match-case is Python’s structural pattern‑matching feature (introduced in Python 3.10).
Think of it as a much more powerful switch, designed to match not just values but also shapes and structures of data.

Many people think that match-case is a fancy way of doing if statements. You can, but its purpose goes beyond that.

1. Basic idea (value matching)

At its simplest, it looks like a switch statement in other languages:

def http_status_message(status):
    match status:
        case 200:
            return "OK"
        case 404:
            return "Not Found"
        case 500:
            return "Server Error"
        case _:
            return "Unknown status"

Key points

• match evaluates once.
• Cases are tried top‑to‑bottom.
• _ is the wildcard (default case).

Equivalent if version:

def http_status_message(status):
    if status == 200:
        return "OK"
    elif status == 404:
        return "Not Found"
    elif status == 500:
        return "Server Error"
    else:
        return "Unknown status"

For simple look‑ups a dictionary may be clearer:

def http_status_message(status):
    messages = {
        200: "OK",
        404: "Not Found",
        500: "Server Error",
    }
    return messages.get(status, "Unknown status")

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2. Structural pattern‑matching (shapes and structures of data)

Tuple / sequence matching

point = (0, 5)

match point:
    case (0, y):
        print(f"On Y axis at y={y}")
    case (x, 0):
        print(f"On X axis at x={x}")
    case (x, y):
        print(f"At ({x}, {y})")

• (0, y) means the first element must be 0; the second element is captured as y.
• This matches the shape of the object, not just equality.

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3. Matching lists with rest (*)

numbers = [1, 2, 3, 4]

match numbers:
    case [first, *rest]:
        print(first, rest)

• *rest captures the remaining elements.
• It can appear only once per pattern.

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4. Type and class matching

Simple type matching

def handle(value):
    match value:
        case int():
            print("Integer")
        case str():
            print("String")
        case list():
            print("List")

Class pattern matching

class User:
    def __init__(self, name, is_admin):
        self.name = name
        self.is_admin = is_admin

user = User("Alice", True)

match user:
    case User(name=name, is_admin=True):
        print(f"Admin: {name}")
    case User(name=name):
        print(f"User: {name}")

• Checks that the object is an instance of User and then matches its attributes.

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5. Guards (if inside case)

Sometimes you need an additional condition:

match value:
    case int(x) if x > 0:
        print("Positive integer")
    case int(x):
        print("Non‑positive integer")

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6. OR patterns (|)

match command:
    case "start" | "run" | "go":
        print("Starting…")
    case "stop" | "quit":
        print("Stopping…")

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7. Dict (mapping) matching

data = {"type": "error", "code": 404}

match data:
    case {"type": "error", "code": code}:
        print(f"Error code {code}")

• Extra keys are allowed by default; only the listed keys must match.

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Takeaway

• match-case asks: “Does this value have this shape?”
• if asks: “Is this condition true?”

Extra reading