[Python-Dev] Informal educator feedback on PEP 572 (was Re: 2018 Python Language Summit coverage, last part) (original) (raw)

Rob Cliffe rob.cliffe at btinternet.com
Mon Jul 2 17:46:56 EDT 2018

On 02/07/2018 19:19, Guido van Rossum wrote:

Thank you all. I will accept the PEP as is. I am happy to accept clarification updates to the PEP if people care to submit them as PRs to the peps repo (https://github.com/python/peps), and that could even (to some extent) include summaries of discussion we've had, or outright rejected ideas. But even without any of those I think the PEP is very clear so I will not wait very long (maybe a week). It's late to raise this, but what exactly are the objections to the syntax         expr -> name  # or variations such as  expr => name instead of         name := expr

The PEP mentions that this syntax does not have a problem that "as" does, but does not list any downsides of it. It conforms to left-to-right evaluation, where name:=expr does not. It (I would argue) reduces the asymmetry of the first use of a sub-expression in cases such as     [ ( (f(x) -> y)2, y3, y4) for x in iterable ] vs     [ ( (y := f(x))2, y3, y4) for x in iterable ] because the first "y" is closer to the way it is used, viz "**2".

Regards Rob Cliffe

More information about the Python-Dev mailing list