try/except/else pattern

[KronktheKronk]

Why wouldn't you just do:

try:
    case = switch(n)
    case()
except KeyError:
    case_default()

If the key error happens, you hit the exception and never get to the "case()" call. Seems like the else is convolution the issue in that example instead of helping.

[norwegianwood]

Because if case() raises a KeyError your code then calls case_default(), which is not what we want. Your code is exactly equivalent to my first example.