Python logical `and` returning wrong results comparing lists

Question

y1 = [True, True, False, False]
y2 = [False, True, True, False]
y3 = y1 and y2

print(y3)
>>> [False, True, True, False]

What is going on here? the third item in the operation is False and True and this results in True?

Answer 1

X and Y evalutes to:

• X (if X is falsey)
• Y (if X is truthy)

Any nonempty list is truthy.

So if

y1 = [True, True, False, False]

and

y2 = [False, True, True, False]

then y1 and y2 evaluates to y2, which is [False, True, True, False].

If you want to and individual elements of your lists, you can do it with zip and a list comprehension:

y3 = [x1 and x2 for x1,x2 in zip(y1,y2)]