This is a chained comparison. You may have known that you can do
1 < 2 < 3
in Python, and it's equivalent to (1 < 2) and (2 < 3). (Or maybe you didn't. Now you know.) Well, the same thing applies to in and ==.
5 in [1, 2, 3, 4] == False
is equivalent to
(5 in [1, 2, 3, 4]) and ([1, 2, 3, 4] == False)
Since [1, 2, 3, 4] is not equal to False, the whole expression evaluates to False.
