On Fri, Apr 12, 2019 at 11:31 PM Victor Stinner <vstin...@redhat.com> wrote: > > Nice optimization! I have questions on the proposed API. > > > with_values(self, iterable, /) > > Create a new dictionary with keys from this dict and values from > > iterable. > > > > When length of iterable is different from len(self), ValueError is > > raised. > > This method does not support dict subclass. > > In short, mydict.with_values(values) behaves as > dict(zip(mydict.keys(), values)), but is more efficient?
Yes. But unlike zip, keys() and values must have exactly same length. > > The method rely on the fact that dict is preserving key insertion order, > right? > Yes. > > This might be usable for: > > > > * csv.DictReader > > * namedtuple._asdict() > > * DB-API 2.0 implementations: (e.g. DictCursor of mysqlclient-python) > > I guess that a new dict constructor taken keys and values like > dict.from_keys_and_values(keys, values) would work, but would not > benefit from the dict key-sharing optimization? > I don't like more overloading. And this API is specialized to build multiple dicts, not one dict. So I want to have dedicated API for it. > Would it be possible to implement the key-sharing optimization using a > dict.from_keys_and_values(mydict.keys(), values) method: detect that > keys are owned by a dict, and so create a new dict linked to the keys > dict? A dict view contains a reference to the iterated dict > (dictiterobject.di_dict). I think it is possible. > > I'm fine with dict.with_values() API, but I'm asking if it could be > written differently. > > Victor I implemented it as instance method of dict because it may modify the dict internally (at first invocation). -- Inada Naoki <songofaca...@gmail.com> _______________________________________________ Python-Dev mailing list Python-Dev@python.org https://mail.python.org/mailman/listinfo/python-dev Unsubscribe: https://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
