Boolean confusion

[Peter Hansen]

Frantisek Fuka wrote:
> 
> Can anyone please explain why these two give different results in Python
> 2.3?
> 
>  >>> 'a' in 'abc' == 1
> False
>  >>> ('a' in 'abc') == 1
> True
> 
> I know it's not a good idea to compare boolean with Integer but that's
> not the answer to my question.

Hmm....

>>> dis.dis(lambda : 'a' in 'abc' == 1)
  1           0 LOAD_CONST               1 ('a')
              3 LOAD_CONST               2 ('abc')
              6 DUP_TOP
              7 ROT_THREE
              8 COMPARE_OP               6 (in)
             11 JUMP_IF_FALSE           10 (to 24)
             14 POP_TOP
             15 LOAD_CONST               3 (1)
             18 COMPARE_OP               2 (==)
             21 JUMP_FORWARD             2 (to 26)
        >>   24 ROT_TWO
             25 POP_TOP
        >>   26 RETURN_VALUE
>>> dis.dis(lambda : ('a' in 'abc') == 1)
  1           0 LOAD_CONST               1 ('a')
              3 LOAD_CONST               2 ('abc')
              6 COMPARE_OP               6 (in)
              9 LOAD_CONST               3 (1)
             12 COMPARE_OP               2 (==)
             15 RETURN_VALUE

Judging by the "odd" (unexpected) code in the first example, 
"A in B == C" is actually doing operator chaining, in a manner
similar to "A < B < C".  Since 'a' is in 'abc' but 'abc' is 
not equal to 1, the chained test fails.

I can't comment further on the validity of such a thing, but 
there you have it.

-Peter