The challenge with anything like result = default if bar is None else bar or result = bar if bar else default or even result = bar is None ? default : bar is that sure default is only evaluated once - but in all cases 'bar' is evaluated twice, and if bar is a function call then no parser is clever enough to diagnose all possible side effects of calling bar() twice, or even detect that bar can be cached, so it will always be called twice. In Python then a better way might be result = temp := bar() if temp else default This way only bar() and default are evaluated and invoked once. ------ Original Message ------ From: "Rob Cliffe via Python-ideas" <python-ideas@python.org> To: "Dom Grigonis" <dom.grigonis@gmail.com>; "Jothir Adithyan" <adithyanjothir@gmail.com> Cc: python-ideas@python.org Sent: Monday, 17 Jul, 23 At 16:09 Subject: [Python-ideas] Re: Proposal for get_or function in Python dictionaries On 15/07/2023 21:08, Dom Grigonis wrote: Just to add. I haven’t thought about evaluation. Thus, to prevent evaluation of unnecessary code, introduction of C-style expression is needed anyways: 1. result = bar is None ? default : bar The below would have to evaluate all arguments, thus not achieving benefits of PEP505. 2. result = ifelse(bar is None, default, bar) So I would vote for something similar to: result = bar is None ? default : bar Where default and bar is only evaluated if needed. Although not to the extent as initially intended, it would offer satisfiable solutions to several proposals. Well, default is only evaluated if needed; bar is always evaluated. What is wrong with the Python equivalent result = default if bar is None else bar or if you prefer result = bar if bar is not None else default Perhaps you didn't know about this construction? It does exactly the same as the C version and is more readable. Or am I missing something? Best wishes Rob Cliffe _______________________________________________ Python-ideas mailing list -- python-ideas@python.org To unsubscribe send an email to python-ideas-leave@python.org https://mail.python.org/mailman3/lists/python-ideas.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/4QBAYB... <https://mail.python.org/archives/list/python-ideas@python.org/message/4QBAYB...> Code of Conduct: http://python.org/psf/codeofconduct/ <http://python.org/psf/codeofconduct/> -- <br>Anthony Flury<br>anthony.flury@btinternet.com