It really ius frustrating how often we repeat entire conversations on this list :-(
But last time, one of the use cases was "get a random item from a dict", and there really is not a terribly easy (and efficient) way to do that now. Anyway, I do see the benefit of adding first() to itertools -- there really is a key problem with: next(iter(an_iterable)) for newbies -- you can get really really far in Python without ever having to call either next() or iter(). Sure, if it's a recipe, people can use it without really understanding it, but having an easy and obvious solution would be nice. NOTE: I actually use this as a teaching moment in my intro to Python class: we have an assignment where there is a need to grab an arbitrary (not necessarily random) item from a dict (without removing it). most students come up with something like: random.choice(list(the_dict.items())) which works fine for any but the largest of dicts, but is not an optimum solution. I don't think anyone has ever come up with next(iter(the_dict.items)) on their own. So I have a little lesson where I run through the options, and use it as a chance to introduce the iterator protocol. So it's a good teaching moment, but not a great example of how Python usually has an easy and obvious way to do seemingly simple operations. -CHB On Thu, Oct 7, 2021 at 12:44 AM Stephen J. Turnbull < stephenjturnb...@gmail.com> wrote: > Finn Mason writes: > > > We don't need people writing `next(iter(iterable))` just to get the > > first item. > > We already don't need that. `sequence[0]` and `next(iterator)` do the > trick. > > You only need `next(iter(iterable))` if you need all three of > > - an expression (`for first in iterable: break` gives the other two), > - efficient (although the difference with the `for` idiom should > usually be irrelevant) > - polymorphic over sequences and iterators (both special notations are > more efficient expressions). > > and it makes it explicit that that's what you're after. > > At least for beginners, putting this idiom in the Tutorial is probably > the best idea. With the exception of wacko iterables that define > `__next__` but not `__iter__` (which `first` could take care of, but > do we really want to do that? I guess we should if we're going to > define `first`), not only is the idiom the efficient polymorphic > expression, but to understand why it works teachs a lot about > iterables vs. iterators vs. sequences. > > _______________________________________________ > 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/5LQ5TIEDK3PGYB5CYD4GZ7ZMZE7YVWXY/ > Code of Conduct: http://python.org/psf/codeofconduct/ > -- Christopher Barker, PhD (Chris) Python Language Consulting - Teaching - Scientific Software Development - Desktop GUI and Web Development - wxPython, numpy, scipy, Cython
_______________________________________________ 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/ROO4WUKQHZPDAVEYC3RGX2FXXQVKDJT5/ Code of Conduct: http://python.org/psf/codeofconduct/
