Seemingly odd 'is' comparison.

[Duncan Booth]

Boris Borcic <bborcic at gmail.com> wrote:
> Arnaud Delobelle wrote:
>> Whereas when "3.0*1.0 is 3.0" is evaluated, *two* different float
>> objects are put on the stack and compared (LOAD_CONST 3 / LOAD_CONST
>> 1 / COMPARE_OP 8).  Therefore the result is False.
> 
> Looks good, but doesn't pass the sanity check ;) Consider
> 
> >>> def f():
>      return 3 is 3, 3*1 is 3
> 
> >>> import dis
> >>> dis.dis(f)
>    2           0 LOAD_CONST               1 (3)
>                3 LOAD_CONST               1 (3)
>                6 COMPARE_OP               8 (is)
>                9 LOAD_CONST               3 (3)
>               12 LOAD_CONST               1 (3)
>               15 COMPARE_OP               8 (is)
>               18 BUILD_TUPLE              2
>               21 RETURN_VALUE
> >>> f()
> (True, True)
> 

s/different/possibly different depending on implementation details/

Arnaud's point remains valid: in the first comparison you can see that the 
same object is used, in the second case all bets are off.