frozenset can be altered by |=

[Marco Sulla]

Yes, and you do this regularly. Indeed integers, for example, are immutables and

a = 0
a += 1

is something you do dozens of times, and you simply don't think that
another object is created and substituted for the variable named `a`.

On Mon, 22 Nov 2021 at 14:59, Chris Angelico <rosuav at gmail.com> wrote:
>
> On Tue, Nov 23, 2021 at 12:52 AM David Raymond <David.Raymond at tomtom.com> wrote:
> > It is a little confusing since the docs list this in a section that says they don't apply to frozensets, and lists the two versions next to each other as the same thing.
> >
> > https://docs.python.org/3.9/library/stdtypes.html#set-types-set-frozenset
> >
> > The following table lists operations available for set that do not apply to immutable instances of frozenset:
> >
> > update(*others)
> > set |= other | ...
> >
> >     Update the set, adding elements from all others.
>
> Yeah, it's a little confusing, but at the language level, something
> that doesn't support |= will implicitly support it using the expanded
> version:
>
> a |= b
> a = a | b
>
> and in the section above, you can see that frozensets DO support the
> Or operator.
>
> By not having specific behaviour on the |= operator, frozensets
> implicitly fall back on this default.
>
> ChrisA
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