Interview gone wrong

I use tic tac toe as one of the interview questions, the logic is straightforward and it helps to judge things like code quality / speed / conciseness.

The surprising comparison#

One candidate who was a Python developer wrote something like this:

if (cell[0][0] == cell[1][1] == cell[2][2]):
    return Winner

At first I thought this was logically flawed. Since cell[x][y] contains characters ('-', 'X', or 'Y'), the expression True == cell[2][2] would return False in JavaScript.

Python's chained expressions#

However, Python handles this differently through chained expressions. Python transforms the above into:

if ((cell[0][0] == cell[1][1]) and (cell[1][1] == cell[2][2])):
    return Winner

The code is indeed correct. Python has yet another way to confuse us all.