what does is ?

[Jonas Geiregat]

Gerhard Häring wrote:

> Padraig Brady  wrote:
>
> >Gerhard Häring wrote:
> >
> >>Jonas Geiregat  wrote:
> >>
> >>
> >>>I saw something
> >>>import string
> >>>string._StringType is str
> >>>what does this specially that IS
> >>
> >>The "is" operator compares object *identity*, rather than equality, 
> which
> >>the "==" operator does.
> >
> >Well why does the following happen on 2.2?
> >Is Python being clever about merging variables?
> >
> >s1="123"
> >s2=s1[:]
> >s1 is s2 #true?
>
>
> Yes. Certain strings (not all) are being "interned". And certain ints 
> (not all)
> are interned, too:
>
>  >>> a = 5
>  >>> b = 10/2
>  >>> a is b
>  1
>  >>> x = 1000000000000
>  >>> y = 2000000000000 / 2
>  >>> x is y
>  0
>
> But it seems to me that the [:] slicing has an additional 
> optimization, apart
> from interning.

why is x is y 0 and a is b 1
I don't get it it's the same code only different and bigger numbers