Why Does This Not Work As An Array Membership Test?

>>> 5 in [1, 2, 3, 4] == False False I get that this is a bizarre way to test membership, and that >>> 5 not in [1, 2, 3, 4] True is the 'correct' way. What co

Solution 1:

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.