What is a function parameter =[] for?

[Ben Finney]

Steven D'Aprano <steve at pearwood.info> writes:

> On Thu, 26 Nov 2015 09:34 pm, Dave Farrance wrote:
>
>
> > (Conversely, I see that unlike CPython, all PyPy's numbers have
> > unchanging ids, even after exiting PyPy and restarting, so it seems
> > that PyPy's numerical ids are "faked".)
>
> I'm pretty sure that they are faked.

It's still not been expressed what “fake” refers to here. Or, rather,
what “real” thing was being expected, and how these don't qualify.

The object IDs are real IDs, they identify the object, they're not
pretending to be anything other than object IDs, they are perfectly
compliant with the language definition and all the documentation.

What is fake? What “real” thing was expected, and *why* was that
expected?

-- 
 \     “Do unto others twenty-five percent better than you expect them |
  `\      to do unto you. (The twenty-five percent is [to correct] for |
_o__)                            error.)” —Linus Pauling's Golden Rule |
Ben Finney