Is there a function in Python that finds a different unit of a list?

Question

Python

Given a list, let a = [1, 1, 1, 1, 2, 1, 1, 1]. In this list, all elements are the same, except for one (in this case, 2). The question is, is there such a function in python that finds this very element that is different from the rest?

Answer 1

from collections import Counter

rarest = Counter(a).most_common()[-1][0]

Answer 2

rarest =  [y for y in list(set(a)) if len([x for x in a if x == y]) == 1][0]

a.sort(); 
rarest = set(a[:2]) - set(a[-2:])

Answer 3

>>> while min(a) != max(a):
... a1 = a.pop()
...
>>> a1
2
>>>