Replacements for switch statement in Python?

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.

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

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

If you'd like defaults, you could use the dictionary get(key[, default]) function:

def f(x):
    return {
        'a': 1,
        'b': 2
    }.get(x, 9)    # 9 will be returned default if x is not found

I've always liked doing it this way

result = {
  'a': lambda x: x * 5,
  'b': lambda x: x + 7,
  'c': lambda x: x - 2
}[value](x)

From here

In addition to the dictionary methods (which I really like, BTW), you can also use if-elif-else to obtain the switch/case/default functionality:

if x == 'a':
    # Do the thing
elif x == 'b':
    # Do the other thing
if x in 'bc':
    # Fall-through by not using elif, but now the default case includes case 'a'!
elif x in 'xyz':
    # Do yet another thing
else:
    # Do the default

This of course is not identical to switch/case - you cannot have fall-through as easily as leaving off the break statement, but you can have a more complicated test. Its formatting is nicer than a series of nested ifs, even though functionally that's what it is closer to.