New assignmens ...

dn PythonList at
Fri Oct 22 15:41:04 EDT 2021

On 23/10/2021 08.34, Chris Angelico wrote:
> On Sat, Oct 23, 2021 at 6:24 AM Jon Ribbens via Python-list
> <python-list at> wrote:
>> On 2021-10-22, Stefan Ram <ram at> wrote:
>>> Paulo da Silva <p_d_a_s_i_l_v_a_ns at> 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.

ie neither can one use subscripted elements, eg list-elements, as the
LHS of an assignment expression.

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