On Thu, May 7, 2020 at 11:16 AM David Mertz <me...@gnosis.cx> wrote: > > On Wed, May 6, 2020 at 8:37 PM Chris Angelico <ros...@gmail.com> wrote: >> >> > The only precedent that jumps out for me is itertools.chain() and >> > itertools.chain.from_iterable(). It's quite likely that something I don't >> > use much has used the same pattern though. >> >> That's an example of a very common pattern of alternate constructors. > > > The other Chris' comment was: > >> zip.shortest(...) # same as zip(...) / zip.longest(...) / zip.checksame(...) >> I kind of like this -- is there any precedent for it in the standard library? > > > If it's a very common pattern, do you know of any in the standard library > beyond the one I mentioned? Not about bikeshedding the spelling of the > different constructors, but just: > > 1. A callable; > 2. That has one or more functions attached to perform some variation on what > that callable itself does. >
The first one that comes to mind is the datetime types, which have from* methods that construct them from timestamps, strings, etc. A quick search of the cpython/Lib directory shows Decimal.from_float, dict.fromkeys, socket.fromfd, and a bunch of others, all of the basic form "construct one of these things in a slightly different way". On Thu, May 7, 2020 at 11:19 AM Eric V. Smith <e...@trueblade.com> wrote: > I think David is right: itertools.chain.from_iterable() is the only > place I know of with an attribute on a function that's another function. > Alternate constructors are generally classmethods. Not that the > distinction is terribly important, but it is a distinction, and it's > documented differently. What do you mean? Are you saying that itertools.chain is a function but datetime.datetime is a class, and that this is fundamentally different? Because Python disagrees: >>> import itertools, datetime >>> type(itertools.chain), type(datetime.datetime) (<class 'type'>, <class 'type'>) itertools.chain.from_iterable is a classmethod (albeit implemented in C, in current CPython). 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/VMNNBBBGP5VWLCF2FGEQIVS3NVZOTTXH/ Code of Conduct: http://python.org/psf/codeofconduct/
