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[Python-Dev] Is PEP 572 really the most effective way to solve the problems it's targeting?

Steven D'Aprano steve at pearwood.info
Thu Apr 26 20:58:16 EDT 2018 
On Thu, Apr 26, 2018 at 09:36:48AM -0700, Mike Miller wrote:

> However, there were two good questions in this message which I haven't seen 
> addressed yet:
> 
>     - How are other modern languages solving this issue?
>     - How does this new construct intersect with typing functionality?

What counts as a modern language? Less than five years old? Less than 
fifty years old? Are Javascript, Ruby and R modern? They all support 
assignment as expressions.

I think Koitlin, Rust and Go prohibit assignment as expressions.

Swift assignment evaluates as Void (equivalent to None in Python, I 
guess), so you can use assignment in an expression but it returns 
nothing and only operates by side-effect.

As far as type hints go, I think that if you need explicit type hints in 
the middle of an expression, it's a bad idea and you ought to pull it 
out as a separate statement. That applies regardless of whether that 
expression involves binding or not.


-- 
Steve
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