Python: return the index of the first element of a list which makes a passed function true

Question

The list.index(x) function returns the index in the list of the first item whose value is x.

Is there a function, list_func_index()

Answer 1

A variation on Alex's answer. This avoids having to type X every time you want to use is_odd or whichever predicate

>>> class X(object):
...     def __init__(self, pred): self.pred = pred
...     def __eq__(self, other): return self.pred(other)
... 
>>> L = [8,10,4,5,7]
>>> is_odd = X(lambda x: x%2 != 0)
>>> L.index(is_odd)
3
>>> less_than_six = X(lambda x: x<6)
>>> L.index(less_than_six)
2