Reference

[Ben Finney]

Marko Rauhamaa <marko at pacujo.net> writes:

> Say I implement Python. Say I returned a random number for id(), how
> would that violate the language spec?

You could do that, certainly. So long as that randomly-chosen integer
was always the same for every object, and never the same for any other
concurrently-existing object, it can just as well be assigned randomly.

If you're saying that your implementation of ‘id(foo)’ would return a
*different* integer when called at different times for the same object,
then yes, that violates the specification for that function.

> It would violate the spec. But there would have to be a paragraph in
> the specification that was violated or a reference test case that
> failed.

Yes. It would violate this paragraph:

    Every object has an identity, a type and a value. An object’s
    identity never changes once it has been created […] the id()
    function returns an integer representing its identity.

    <URL:http://docs.python.org/3/reference/datamodel.html>

Again, I ask you to read these documents for comprehension.

> For example, this test would demonstrate obviously invalid behavior:
>
>    >>> print(id(x))
>    129
>    >>> print(id(x))
>    201

Yes. That violates the paragraph above, and so that implementation is
not compliant with the Python language reference.

-- 
 \       “I watched the Indy 500, and I was thinking that if they left |
  `\         earlier they wouldn't have to go so fast.” —Steven Wright |
_o__)                                                                  |
Ben Finney