Odd Operator Precedence/associativity Behaviour

How is it that, in Python 2.7, the following True == 'w' in 'what!?' behaves differently than both (True == 'w') in 'what!?' and True == ('w' in 'what!?') ? >>> True ==

Solution 1:

In Python, comparisons can be chained together:

Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once (but in both cases z is not evaluated at all when x < y is found to be false).

So your code is actually equivalent to

>>> (True == 'w') and ('w'in'what!?')
False

Solution 2:

Let's take a look:

>>>import ast>>>ast.dump(ast.parse("""True == 'w' in 'what!?'""", mode='eval'))
"Expression(body=Compare(left=Name(id='True', ctx=Load()), ops=[Eq(), In()],
comparators=[Str(s='w'), Str(s='what!?')]))"

This is a chained comparison:

Comparisons can be chained arbitrarily, e.g., x < y <= z is equivalent to x < y and y <= z, except that y is evaluated only once [...]