Tuple assignment and generators?

[Diez B. Roggisch]

> 
> I was just at a point when I thought I learned something but got
> confused again after trying the following and unfortunately didn't
> find an answer in the docs.
> 
>>>> a = 10
>>>> b = 10
>>>> id(a)
> 134536516
>>>> id(b)
> 134536516
> 
> So the two memory addesses are the same, but
> 
>>>> a = 10000
>>>> b = 10000
>>>> id(a)
> 134604216
>>>> id(b)
> 134604252
> 
> and they are not the same (I restarted the interpreter between the two
> cases). So how is this now? Sorry if it's too trivial, but I simply
> don't get it.

It's an optimization scheme that will cache number objects up to a certain
value for optimized reuse. However this is impractical for larger numbers -
you only hold a table of lets say 1000 or so objects. Then the look up of
one of those objects is extremely fast, whereas the construction of
arbitrary numbers is somewhat more expensive.

And as "is" is the operator for testing if objects are identical and _not_
the operator for testing of equality (which is ==), the above can happen.
And is totally irrelevant from a practical POV (coding-wise that is - it
_is_ a relevant optimization).

Diez