Why does `if None.__eq__(“a”)` seem to evaluate to True (but not quite)?

Question

If you execute the following statement in Python 3.7, it will (from my testing) print b:

if None.__eq__(\"a\"):
    print(\"b\")

Answer 1

Why?

It returns a NotImplemented, yeah:

>>> None.__eq__('a')
NotImplemented
>>> 

But if you look at this:

>>> bool(NotImplemented)
True
>>> 

NotImplemented is actually a truthy value, so that's why it returns b, anything that is True will pass, anything that is False wouldn't.

How to solve it?

You have to check if it is True, so be more suspicious, as you see:

>>> NotImplemented == True
False
>>> 

So you would do:

>>> if None.__eq__('a') == True:
    print('b')


>>> 

And as you see, it wouldn't return anything.