On Thu, Jun 17, 2021 at 9:46 AM Oliver Margetts <oliver.marge...@gmail.com> wrote: > > > I'm not sure why it doesn't special-case it to "".join() > One reason might be because you'd have to read the entire iterator to know if > it really was only strings. So there are concerns with generators which > complicate things a fair bit >
Perhaps, but I'm not sure what's actually being verified here. The check is applied to the start parameter. (If you don't set start, you'll get a TypeError for trying to add an int and a str.) In fact, if you disrupt that check, sum() is quite happy to add strings together - with potentially quadratic runtime: >>> class AdditiveIdentity: ... def __add__(self, other): return other ... >>> sum(["Hello ", "world!"], start=AdditiveIdentity()) 'Hello world!' Either way, if there's a non-str part way through, it'll bomb when it reaches that. I've no idea what the reason is for not bouncing it straight into join(), but I'm sure there must be one. ChrisA _______________________________________________ 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/DIUAQZMWBFLUEBO4A66POK2FXOAI5TDD/ Code of Conduct: http://python.org/psf/codeofconduct/
