python - How do I name a function that takes an object `A` and a set `{A, B}` as arguments, then returns `B`? -

what name following function (as implemented in python)?

def a_function(element, a_set):     if a_set[0] == element:         return a_set[1]     if a_set[1] == element:         return a_set[0]  assert 'a' == a_function('b', ['a', 'b']) 

i use different function name, different argument names , docstring make clear what's going on, like:

def get_other(current, both):     """return element 'both' not 'current'."""     ... 

note both implies pair without long-winded, , doesn't specify type required.

you can use own implementation or joel's; long function says, doesn't matter how it's implemented (barring performance concerns, edge cases, etc.).

however, work non-indexable containers (like set, or keys of dict) without having explicitly test both is, go for:

def get_other(current, both):     """return element 'both' not 'current'."""     item in both:         if item != current:             return item 

indeed, if len(both) > 2, return first item in isn't equal current - can add checks if not desired behaviour.