30-seconds-of-code/snippets/when.md

title, type, tags, cover, dateModified

title	type	tags	cover	dateModified
Apply function when true	snippet	function	interior-10	2020-11-09T23:56:11+02:00

Tests a value, x, against a testing function, conditionally applying a function.

• Check if the value of predicate() is True for x and if so call when_true(), otherwise return x.

def when(predicate, when_true):
  return lambda x: when_true(x) if predicate(x) else x

double_even_numbers = when(lambda x: x % 2 == 0, lambda x : x * 2)
double_even_numbers(2) # 4
double_even_numbers(1) # 1