Python Match-Case Statements

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Match-case statement (switch): An alternative to using many ‘elif’ statements. Code is executed is a value matches a ‘case’.
Benefits: cleaner code with more readable syntax.

A match statement takes an expression and compares its value to successive patterns given as one or more case blocks.

Specifically, pattern matching operates by:

1. using data with type and shape (the subject)
2. evaluating the subject in the match statement
3. comparing the subject with each pattern in a case statement from top to bottom until a match is confirmed.
4. executing the action associated with the pattern of the confirmed match

If an exact match is not confirmed, the last case, a wildcard “_” (underscore), if provided, will be used as the matching case. If an exact match is not confirmed and a wildcard case does not exist, the entire match block is a no-op.

Below we a function with one parameter (day) – (day) will be a number 1 – 7, the function will return the day of the week.

def day_of_week(day):
    if day == 1:
        return "It is a Sunday"
    elif day == 2:
        return "It is a Monday"
    elif day == 3:
        return "It is a Tuesday"
    elif day == 4:
        return "It is a Wednesday"
    elif day == 5:
        return "It is a Thursday"
    elif day == 6:
        return "It is a Friday"
    elif day == 7:
        return "It is a Saturday"
    else:
        return "Not a valid day"

print(day_of_week(3))

An alternative way to achieve the same output that is cleaner and easier to read is to use a match case:

def is_weekend(day):
    match day:
        case "Sunday":
            return True
        case "Monday":
            return False
        case "Tuesday":
            return False
        case "Wednesday":
            return False
        case "Thursday":
            return True
        case "Friday":
            return False
        case "Saturday":
            return True
        case _:
            return False

print(is_weekend("Sunday"))

There is a lot of repetition here, we can use the OR logical operator “| = or” to clean up this code:

def is_weekend(day):
    match day:
        case "Saturday" | "Sunday":
            return True
        case "Monday" | "Tuesday" | "Wednesday" | "Thursday" | "Friday":
            return False
        case _:
            return False

print(is_weekend("Monday"))

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