Boolean Operators in Python Aren’t What You Think

There’s more to these little guys than meets the eye

Photo by Mitchell Luo on Unsplash

I consider myself a decent Python programmer. I’ve worked with the language extensively in the past and it’s the one I generally feel most comfortable using.

But even well within the cozy confines of our comfort zones, every now and then, we all come across energizingly unfamiliar “huh” moments. Recently, I had one such moment and it came from where one might least expect it: good old Boolean operators.

You see, until that point, I was under the impression that the expressions True and False, "abc" and "", and None or 0 would all evaluate to False, owing to the fact that Python interprets False, None, empty strings, numeric zero of all types, as well as other values as false.

And why wouldn’t I think this? After all, we’ve been using if statements forever and they’ve never disappointed.

if 1 and 0:
    print("You will never see this...")
if 1 or 0:
    print("But this you will see!")

Obviously, 1 and 0 is equivalent to False and 1 or 0 to True, right?

But here’s the catch: The fact that Python interprets certain non-Boolean values (like 1 or "") as True or False when presented in a Boolean context (e.g. when used in…