match and case

Big idea

match compares one value against a list of patterns and runs the first case that fits — a tidy replacement for a long chain of elif x == ....

The idea

day = 3
match day:
    case 1:
        print("Monday")
    case 2:
        print("Tuesday")
    case 3:
        print("Wednesday")
    case _:
        print("Some other day")

output
Wednesday

• match day: — the value to check.
• case 3: — "if it's 3, run this".
• case _: — the wildcard: matches anything. Put it last, as the "otherwise".

Only one case runs, and there's no "falling through" to the next case as in C's switch — no break needed.

(match arrived in Python 3.10. Older Pythons don't have it; there you'd write if/elif.)

Several values in one case

| means "or" inside a pattern:

day = "sat"
match day:
    case "sat" | "sun":
        print("Weekend")
    case "mon" | "tue" | "wed" | "thu" | "fri":
        print("Weekday")
    case _:
        print("Not a day")

Weekend

Watch it

Patterns with a condition

Add if after a pattern for an extra check — called a guard. A plain name like n matches anything and captures it:

for n in [-4, 0, 7]:
    match n:
        case 0:
            print("zero")
        case n if n < 0:
            print("negative")
        case _:
            print("positive")

output
negative
zero
positive

Matching shapes

match really shines when the value has a structure, like a list of words. Each pattern can pull the pieces out:

for command in ["go north", "look", "take lamp", "dance"]:
    match command.split():
        case ["go", direction]:
            print("You walk", direction)
        case ["look"]:
            print("You see a dark room")
        case ["take", item]:
            print("You pick up the", item)
        case _:
            print("I don't understand")

output
You walk north
You see a dark room
You pick up the lamp
I don't understand

["go", direction] matches a two-word list whose first word is "go", and stores the second word in direction. (Lists get their own module next — this is a preview of why they're useful.)

day = 5
match day:
    case _:
        print("Unknown day")
    case 5:
        print("Friday")

output
Friday

The wildcard matches everything, so a case after it can never run. Python actually refuses this with a SyntaxError: wildcard makes remaining patterns unreachable. Move case _ to the end.

Think of it like

A post-office sorting desk. Each parcel is checked against the labels on the bins — "London", "Paris", "anything else" — and goes into the first bin that matches.

Key terms

• match / case — Compare a value against patterns; run the first case that fits.
• Wildcard (_) — A pattern that matches anything.
• Guard — An if condition attached to a case.