[Python-Dev] PEP 572: Do we really need a ":" in ":="?

[Yury Selivanov]

I think I tried a variation of your proposal here
https://mail.python.org/pipermail/python-dev/2018-April/152939.html
and nobody really liked it.

Yury
On Thu, Jul 5, 2018 at 7:44 PM Alexander Belopolsky
<alexander.belopolsky at gmail.com> wrote:
>
> I wish I had more time to make my case, but with the PEP 572 pronouncement imminent, let me make an attempt to save Python from having two assignment operators.
>
> I've re-read the PEP, and honestly I am warming up to the idea of allowing a limited form of assignment in expressions.  It looks like in the current form, the PEP supports only well-motivated cases where the return value of the assignment expression is non-controversial.  It also appears that there are no cases where = can be substituted for := and not cause a syntax error.  This means that ":" in ":=" is strictly redundant.
>
> Interestingly, Python already has a precedent for using redundant ":" - the line-ending ":" in various statements is redundant, but it is helpful both when reading and writing the code.
>
> On the other hand, ':' in ':=' looks like an unnecessary embellishment.  When we use ':=', we already know that we are inside an expression and being inside an expression is an obvious context for the reader, the writer and the interpreter.
>
> I also believe, allowing a limited form of assignment in expressions is a simpler story to tell to the existing users than an introduction of a new operator that is somewhat like '=', but cannot be used where you currently use '=' and only in places where '=' is currently prohibited.
>
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-- 
         Yury