[Python-Dev] Proposal: dict.with_values(iterable)

Inada Naoki songofacandy at gmail.com
Fri Apr 12 12:17:10 EDT 2019

On Sat, Apr 13, 2019 at 12:38 AM Serhiy Storchaka <storchaka at gmail.com> wrote:
> It looks contrary to simplification made in Python 3 when we get rid of
> some more efficient lists in favor of more general iterators.

Yes.  This is API for special use case creates many dict having
same keys, like csv.DictReader.
It is not good design for general purpose.

strings module has strings.Template class.  But I don't want to add
dicts module.
Maybe, collections.DictBuilder may be another option.  e.g.

>>> from collections import DictBuilder
>>> builder = DictBuilder(tuple("abc"))
>>> builder.build(range(3))
{"a": 0, "b": 1, "c": 2}

> If this is a common case we can add an invisible optimization for
> dict(zip(keys, values)), especially if keys is a key-sharing dictionary.
> This will benefit all users without the need to rewrite the code to use
> the new special method.

But this optimization may slow down when creating one dict...

> The interface of dict is already overloaded. It contains many methods
> which most users use rarely (and therefore which are not kept in the
> working set of memory).


Inada Naoki  <songofacandy at gmail.com>

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