Why does this boolean expression evaluate to False? [duplicate]

Question

Can someone explain to me why the Python interpreter evaluates this expression to be False?

1 in [1] == True

I would expect that 1 in [1] would evaluate to True, and obviously True == True would be True. However this isn't what happens - the expression is False. Why does this happen?

Answer 1

== and in are both comparison operators. And when you have multiple comparison operators like this, Python considers it a chained comparison. For example, 1 < x < 10 is equivalent to 1 < x and x < 10.

In your case, 1 in [1] == True is equivalent to (1 in [1]) and ([1] == True), which evaluates to False.