On Tue, Jun 14, 2022 at 11:59:44AM +0100, Rob Cliffe via Python-ideas wrote:

> I used to prefer `:=` but coming back to this topic after a long
> interval I am happy with `=>` and perhaps I even like it more, Chris.😁
> The PEP status is "Draft".  What are the chances of something happening
> any time soon, i.e. the PEP being considered by the Steering Committee? 

There's no Sponsor, so it isn't being considered by the SC. That much is
objectively true.

Beyond that, the following is all my personal opinion, and should not be
taken as definitive or official in any way. Importantly, I have *not*
read back through the entire thread to refresh my memory. However, I
have re-read the PEP in detail.

There's no consensus that this feature is worth the added complexity, or
even what the semantics are. The PEP punts on the semantics, saying that
the behaviour may vary across implementations.

There's no consensus on the syntax, which may not matter, the Steering
Council can make the final decision if necessary. But with at least four
options in the PEP it would be good to narrow it down a bit. No soft
keywords have been considered.

In my opinion, there are weaknesses in the PEP:

- lack of any reference to previous discussions;

- no attempt to gather feedback from other forums;

- no review of languages that offer choice of early or late binding;

- little attempt to justify why this is better than the status quo; the
  PEP seems to take the position that it is self-evident that Python
  needs this feature, rather than being a balanced document setting out
  both pros and cons;

- little or no attempt in the PEP to answer objections;

- examples are all chosen to show the feature in the best possible
  light, rather than to show both the good and bad; (e.g. no examples
  show the parameter with annotations)

- failure to acknowledge that at least one of the suggested syntaxes
  is visually ambiguous with existing syntax.

E.g. this would be legal with the PEP's second choice of spelling:

    def func(spam, eggs:=(x:=spam)):

Even if the parser can distinguish the two uses of `:=` there, its
awfully cryptic. In and of itself, that's not necessarily a fatal flaw
(e.g. slicing) but the benefits have to outweigh the negatives, and the
PEP should be a balanced discussion of both.



--
Steve
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