Shouldn’t this go to itertools-ideas? :-) On Mon, Jul 27, 2020 at 13:56 David Mertz <me...@gnosis.cx> wrote:
> I don't like consuming the iterator in the exception case. You might > expect just one, but have a fallback approach for more. You could build the > safer behavior using itertools.tee() or itertools.chain(). > > On Mon, Jul 27, 2020, 3:10 PM Noam Yorav-Raphael <noamr...@gmail.com> > wrote: > >> Hi, >> >> There's a simple function that I use many times, and I think may be a >> good fit to be added to itertools. A function that gets an iterator, and if >> it has exactly one element returns it, and otherwise raises an exception. >> This is very useful for cases where I do some sort of query that I expect >> to get exactly one result, and I want an exception to be raised if I'm >> wrong. For example: >> >> jack = one(p for p in people if p.id == '1234') >> >> sqlalchemy already has such a function for queries: >> https://docs.sqlalchemy.org/en/13/orm/query.html#sqlalchemy.orm.query.Query.one >> >> This is my implementation: >> >> def one(iterable): >> it = iter(iterable) >> try: >> r = next(it) >> except StopIteration: >> raise ValueError("Iterator is empty") >> try: >> next(it) >> except StopIteration: >> return r >> else: >> raise ValueError("Iterator has more than one item") >> >> What do you think? >> >> Thanks, >> Noam >> _______________________________________________ >> Python-Dev mailing list -- python-dev@python.org >> To unsubscribe send an email to python-dev-le...@python.org >> https://mail.python.org/mailman3/lists/python-dev.python.org/ >> Message archived at >> https://mail.python.org/archives/list/python-dev@python.org/message/D52MPKLIN4VEXBOCKVMTWAK66MAOEINY/ >> Code of Conduct: http://python.org/psf/codeofconduct/ >> > _______________________________________________ > Python-Dev mailing list -- python-dev@python.org > To unsubscribe send an email to python-dev-le...@python.org > https://mail.python.org/mailman3/lists/python-dev.python.org/ > Message archived at > https://mail.python.org/archives/list/python-dev@python.org/message/N75BG5XVXKENVWAPU4K5UP4I3DKXTITO/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- --Guido (mobile)
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