> On Jun 22, 2022, at 2:12 PM, Paul Moore <p.f.mo...@gmail.com> wrote: > > On Wed, 22 Jun 2022 at 18:35, David Mertz, Ph.D. <david.me...@gmail.com> > wrote: >> >> Hi Martin, >> >> Short answer: yes, I agree. >> Slightly longer: I would be eternally grateful if you wish to contribute to >> the PEP with any such expansion of the Motivation and Expansion. > > One concern I have, triggered by Martin's Dask, PySpark and Django > examples, is that we've seen proposals in the past for "deferred > expression" objects that capture an unevaluated expression, and make > its AST available for user code to manipulate. The three examples here > could all use such a feature, as could other ORMs (and I'm sure there > are other use cases). This is in contrast to your proposal, which > doesn't seem to help those use cases (if it does, I'd like to > understand how). > > The key distinction seems to be that with your proposal, evaluation is > "on reference" and unavoidable, whereas in the other proposals I've > seen, evaluation happens on demand (and as a result, it's also > possible to work with the expression AST *before* evaluation). My > concern is that we're unlikely to be able to justify *two* forms of > "deferred expression" construct in Python, and your proposal, by > requiring transparent evaluation on reference, would preclude any > processing (such as optimisation, name injection, or other forms of > AST manipulation) of the expression before evaluation. > > I suspect that you consider evaluation-on-reference as an important > feature of your proposal, but could you consider explicit evaluation > as an alternative? Or at the very least address in the PEP the fact > that this would close the door on future explicit evaluation models?
Every time I’ve looked at this, I come back to: other than the clunky syntax, how is explicit evaluation different from a zero-argument lambda? Eric _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-le...@python.org https://mail.python.org/mailman3/lists/python-ideas.python.org/ Message archived at https://mail.python.org/archives/list/python-ideas@python.org/message/7OFY7ES6ON3I2QQEVAAATUX2OUHD5L2A/ Code of Conduct: http://python.org/psf/codeofconduct/
