Why does `True == False is False` evaluate to False? [duplicate]

Question

I get some rather unexpected behavior on an expression that works with == but not with is:

>>> (True == False) is False True >>> True == (False is False) True >>> True == False is False False >>> id(True) 8978640 >>> id(False) 8978192 >>> id(True == False) 8978192 >>> id(False is False) 8978640 

Answer 1

Because in fact that's a chained comparison, so

True == False is False 

is equivalent to

(True == False) and (False is False) 

This can be surprising in this case, but lets you write 1 <= x < 4 unlike in other languages like C.