[Python-Dev] PEP 572: Assignment Expressions (original) (raw)

Barry Warsaw barry at python.org
Mon Apr 23 17:19:36 EDT 2018

On Apr 23, 2018, at 13:01, Ethan Furman <ethan at stoneleaf.us> wrote:

On 04/22/2018 10:44 PM, Tim Peters wrote:

I find myself warming more to binding expressions the more I keep them in mind while writing new code.

And I really like the term “binding expressions” because that’s how I think about this feature. I also think it will be easier to explain because “all it does” is bind a value to a name, and to me that’s the most powerful and valuable thing behind this feature.

So I really like being able to make the assignment in the expression, but I have a really hard time parsing it with the name first.

Me too. Plus we already have precedence for spelling name bindings in similar constructs, such as import statements, with statements, and exceptions. It seems like a natural and Pythonic approach to extend that same spelling to binding expressions rather than introducing new, weird, symbols.

I also think it effectively solves the switch-statement problem:

if (get_response() as answer) == 'yes': do_it() elif answer == 'no': skip_it() elif answer == 'maybe' okay_then()

That’s Pythonic enough for jazz!

-Barry

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