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

Brett Cannon brett at python.org
Fri Apr 12 13:16:11 EDT 2019

On Fri, Apr 12, 2019 at 8:35 AM Serhiy Storchaka <storchaka at gmail.com> wrote:

12.04.19 16:44, Inada Naoki пише: > When creating many dicts with same keys, dict need to > lookup internal hash table while inserting each keys. > > It is costful operation. If we can reuse existing keys of dict, > we can skip this inserting cost. > > Additionally, we have "Key-Sharing Dictionary (PEP 412)". > When all keys are string, many dict can share one key. > It reduces memory consumption.

It looks contrary to simplification made in Python 3 when we get rid of some more efficient lists in favor of more general iterators. If this is a common case

I think that "if" is my big sticking point. I don't think I've ever had a need for this and the zip() solution was what I originally thought of when I realized what the method was meant to do (which wasn't obvious to me initially).

This doesn't strike me as needing an optimization through a dedicated method.

-Brett

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.

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).

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