A question on modification of a list via a function invocation

[Chris Angelico]

On Wed, Sep 6, 2017 at 10:11 PM, Rustom Mody <rustompmody at gmail.com> wrote:
> On Wednesday, September 6, 2017 at 5:08:20 PM UTC+5:30, Steve D'Aprano wrote:
>> On Wed, 6 Sep 2017 07:13 pm, Rustom Mody wrote:
>>
>>
>> > Can you explain what "id" and "is" without talking of memory?
>>
>> Yes.
>>
>> id() returns an abstract ID number which is guaranteed to be an integer, and
>> guaranteed to be distinct for all objects which exist at the same time. When an
>> object ceases to exist, its ID number may be re-used.
>>
>> `is` compares the two operands for identity. If the two operands are the same
>> object, `is` returns True, if they are distinct objects, `is` returns False.
>
>>>> a = (1,2)
>>>> b = (1,2)
>>>> a is b
> False
>>>> x = 1
>>>> y = 1
>>>> x is y
> True
>
> a seems to be as 'same' to b as x is to y
> Python seems to think otherwise
>
> Evidently your ‘same’ is not the same as mine??

*facepalm*

I got nothing to say to you. Have you been on this list all this time
and still don't understand that Python sometimes optimizes immutables?

ChrisA