Python · control flow · 3.10+

Match Statement

Compare one value against a list of patterns and run the first case that fits.

Basic match


        # match-case statement
        command = "start"
        match command:
            case "start":
                print("Starting...")
            case "stop":
                print("Stopping...")
            case _:
                print("Unknown")
        # ans: Starting...
command =

How a case is chosen

match status_code:
case 200 | 201:
print("Success")
case 404:
print("Not Found")
case _:
print("Other")
201
status_code =

Cases are tried top to bottom; the first pattern that fits wins and the rest are skipped.

Match with an or pattern


        # multiple values
        status_code = 201
        match status_code:
            case 200 | 201:
                print("Success")
            case 404:
                print("Not Found")
            case _:
                print("Other")
        # ans: Success

Match with a default


        # underscore is the wildcard
        x = 100
        match x:
            case 1:
                print("One")
            case 2:
                print("Two")
            case _:
                print("Default")
        # ans: Default

Match without a default


        # no match, no output
        x = 5
        match x:
            case 1:
                print("One")
            case 2:
                print("Two")
        # ans: (nothing)

Exercises

Predict which case runs, then press → to trace.

Exercise 1


        # what prints?
        x = 2
        match x:
            case 1:
                print("One")
            case 2:
                print("Two")
            case _:
                print("Other")
        # ans: Two

Exercise 2


        # default case?
        x = 100
        match x:
            case 1:
                print("One")
            case _:
                print("Default")
        # ans: Default

Exercise 3


        # multiple values?
        x = 201
        match x:
            case 200 | 201:
                print("Success")
            case _:
                print("Other")
        # ans: Success

Exercise 4


        # no match?
        x = 5
        match x:
            case 1:
                print("One")
            case 2:
                print("Two")
        # ans: nothing (no default, no match)

Exercise 5


        # first match wins?
        x = 1
        match x:
            case 1:
                print("First")
            case 1:
                print("Second")
        # ans: First

Exercise 6


        # match with a string?
        cmd = "quit"
        match cmd:
            case "start":
                result = "Starting"
            case "quit":
                result = "Quitting"
        # ans: result is "Quitting"

Exercise 7


        # wildcard position?
        x = 999
        match x:
            case _:
                print("Any")
            case 999:
                print("999")
        # ans: SyntaxError: case _ must be last

Python refuses to run this: case _ matches everything, so the cases after it could never run.

Exercise 8


        # or pattern?
        x = 503
        match x:
            case 500 | 502 | 503:
                print("Server Error")
        # ans: Server Error

Exercise 9


        # match None?
        x = None
        match x:
            case None:
                print("Is None")
            case _:
                print("Not None")
        # ans: Is None

Exercise 10


        # match with a guard? (advanced)
        x = 15
        match x:
            case n if n > 10:
                print("Big")
            case _:
                print("Small")
        # ans: Big

case n captures the value into n; the guard if n > 10 must also be True.

Remember

Top to bottom

The first case whose pattern fits runs; the rest are skipped.

| means "or"

case 200 | 201: fits either value.

case _

The wildcard fits anything, so it goes last.

No match, no run

Without a wildcard, nothing runs when no case fits.