Why does the expression 0 < 0 == 0 return False in Python?

Question

Looking into Queue.py in Python 2.6, I found this construct that I found a bit strange:

def full(self):
    \"\"\"Return True if the queue is full, False oth         


        

Answer 1

Because

(0 < 0) and (0 == 0)

is False. You can chain together comparison operators and they are automatically expanded out into the pairwise comparisons.

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EDIT -- clarification about True and False in Python

In Python True and False are just instances of bool, which is a subclass of int. In other words, True really is just 1.

The point of this is that you can use the result of a boolean comparison exactly like an integer. This leads to confusing things like

>>> (1==1)+(1==1)
2
>>> (2<1)<1
True

But these will only happen if you parenthesise the comparisons so that they are evaluated first. Otherwise Python will expand out the comparison operators.