New assignmens ...

[Chris Angelico]

On Sat, Oct 23, 2021 at 6:24 AM Jon Ribbens via Python-list
<python-list at python.org> wrote:
>
> On 2021-10-22, Stefan Ram <ram at zedat.fu-berlin.de> wrote:
> > Paulo da Silva <p_d_a_s_i_l_v_a_ns at nonetnoaddress.pt> writes:
> >>Why doesn't this work
> >>      if (self.ctr:=self.ctr-1)<=0:
> >>while this works
> >>      if (ctr:=ctr-1)<=0:
> >
> >   assignment_expression ::=  [identifier ":="] expression,
> >   but the attribute references "self.ctr" is no identifier!
>
> This seems a surprising omission. You'd expect at least 'attributeref'
> and 'subscription' to be allowed, if not the whole of 'target'.

That's not the primary use-case for assignment expressions, and they
were highly controversial. It is much easier to expand it afterwards
than to restrict it, or to have the feature rejected because people
are scared of some small aspect of it.

If you want to propose relaxing the restrictions, make your use-case
and attempt to convince people of the value.

ChrisA