Replacements for switch statement in Python?

Question

I want to write a function in Python that returns different fixed values based on the value of an input index.

In other languages I would use a switch or case statement, but Python does not appear to have a switch statement. What are the recommended Python solutions in this scenario?

Answer 1

Python 3.10 (2021) introduced the match-case statement, which provides a first-class implementation of a "switch" for Python. For example:

def f(x):
    match x:
        case 'a':
            return 1
        case 'b':
            return 2
        case _:
            return 0   # 0 is the default case if x is not found

The match-case statement is considerably more powerful than this simple example.

Documentation:

• match statements (under the "More Control Flow Tools" page)
• The match statement (under "Compound statements" page)
• PEP 634 – Structural Pattern Matching: Specification
• PEP 636 – Structural Pattern Matching: Tutorial

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If you need to support Python ≤ 3.9, use a dictionary instead:

def f(x):
    return {
        'a': 1,
        'b': 2,
    }[x]