[Python-Dev] assignment expressions: an alternative proposal

[Yury Selivanov]

On Tue, Apr 24, 2018 at 9:46 AM, Nick Coghlan <ncoghlan at gmail.com> wrote:
> On 24 April 2018 at 23:38, Yury Selivanov <yselivanov.ml at gmail.com> wrote:
>> I propose to use the following syntax for assignment expressions:
>>
>>     ( NAME = expr )
>>
>> I know that it was proposed before and this idea was rejected, because
>> accidentally using '=' in place of '==' is a pain point in
>> C/C++/JavaScript.
>>
>> That said, I believe we can still use this syntax as long as we impose
>> the following three restrictions on it:
>>
>> 1. Only NAME token is allowed as a single target.
>>
>> 2. Parenthesis are required.
>>
>> 3. Most importantly: it is *not* allowed to mask names in the current
>> local scope.
>
> While I agree this would be unambiguous to a computer, I think for
> most humans it would be experienced as a confusing set of arcane and
> arbitrary rules about what "=" means in Python.

I respectfully disagree.  There are no "arcane and confusing rules"
about "=", it's rather simple:

"=" is always an assignment.
"==" is always an equality check.

Having two assignment operators feels way more arcane to me.
Especially in Python guided by "there should be one way" Zen.

Yury