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pythonbitwise-andlogical-and

Behaviour of bitwise AND and logical AND along with equality operator in Python 3

So I understand bitwise AND is not always safe to use especially if the operands are going to numbers. But am trying to understand what is that tiny subtle reason behind this statement returns to False.

1110010110001000 == 1110010110001000 & 1 == 1 & 1000001000001101 == 1000001000001101 & 1 == 1 --> False

however when I use logical AND operator it returns True which is fairly verbose and clear but trying to understand why the first statement returns False.

and 1110010110001000 == 1110010110001000 and 1 == 1 and 1000001000001101 == 1000001000001101 and 1 == 1 --> True

PS: wasn't able to find any similar QA in my search.

Solution

  • & has higher precedence than ==.

    So this:

    1110010110001000 == 1110010110001000 & 1 == 1 & 1000001000001101 == 1000001000001101 & 1 == 1

    means

    1110010110001000 == (1110010110001000 & 1) == (1 & 1000001000001101) == (1000001000001101 & 1) == 1

    which means

    1110010110001000 == 0 == 1 == 1 == 1

    which means (due to operator chaining)

    (1110010110001000 == 0) and (0 == 1) and (1 == 1) and (1 == 1)

    which is false.

    In summary, don't use & to mean logical and.