[Python-Dev] (name := expression) doesn't fit the narrative of PEP 20

[Steven D'Aprano]

On Thu, Apr 26, 2018 at 05:22:58PM +1200, Greg Ewing wrote:
> Łukasz Langa wrote:
> >What was its own assignment before
> >now is part of the logic test. This saves on vertical whitespace but makes
> >parsing and understanding logic tests harder.
> 
> Another way to say this is that expressions are no longer
> restricted to being trees, but can be general DAGs, which
> require more mental effort to understand.

Is that right? I presume you mean that there can be cycles in 
expressions involving binding-expressions. If not, what do you mean?

Can you give an example of a Python expression, involving PEP 572 
binding-expressions, that is not a tree but a more general DAG or that 
contains cycles?



-- 
Steve