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

Chris Angelico rosuav at gmail.com
Mon Jun 25 15:42:43 EDT 2018

On Tue, Jun 26, 2018 at 5:37 AM, Terry Reedy <tjreedy at udel.edu> wrote:

How loop variables might be isolated without a nested scope: After a comprehension is parsed, so that names become strings, rename the loop variables to something otherwise illegal. For instance, i could become '', just as lambda becomes '' as the name of the resulting function. Expand the comprehension as in Python 2, except for deleting the loop names along with the temporary result name.

Assignment expressions within a comprehension would become assignment expressions within the for loop expansion and would automatically add or replace values in the namespace containing the comprehension. In other words, I am suggesting that if we want name expressions in comprehensions to act as they would in Python 2, then we should consider reverting to an altered version of the Python 2 expansion.

So..... sublocal scopes, like in the earliest versions of PEP 572?

The wheel turns round and round, and the same spokes come up.

ChrisA

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