[Python-Dev] Call for prudence about PEP-572

Mike Miller python-dev at mgmiller.net
Sat Jul 7 23:09:08 EDT 2018

On 2018-07-07 06:09, Giampaolo Rodola' wrote:
>  I initially found myself disliking the idea as a whole but 
> https://github.com/python/cpython/pull/8122 made me (and others) reconsider it 
> quite a bit (see: https://twitter.com/grodola/status/1015251302350245888). 
> PR-8122 clearly shows an improvement in expressiveness and compactness (many 
> folks argue this is too much) 

One of the requirements from the PEP (informing its design) is that there would 
be a significant need and opportunities to use it with multiple and/or compound 

While it may be a function of Victor's choices, from my reading of the pull 
request the vast majority of the improved lines has but a single, simple 
condition such as:

      while (data := f.readframes(1024)):

I believe Giampaolo has a good point.  These expressions are useful, however 
don't seem to have much value outside these examples.

On the subject on imagining how they would be used, suppose we could look at 
JavaScript or other expression-oriented languages for best practices.  Didn't 
find many admonitions however, other than keep it simple:



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