[Python-Dev] Second post: PEP 557, Data Classes

[Brett Cannon]

On Sat, Nov 25, 2017, 14:00 Eric V. Smith, <eric at trueblade.com> wrote:

> The updated version should show up at
> https://www.python.org/dev/peps/pep-0557/ shortly.
>
> The major changes from the previous version are:
>
> - Add InitVar to specify initialize-only fields.
> - Renamed __dataclass_post_init__() to __post_init().
> - Rename cmp to compare.
> - Added eq, separate from compare, so you can test
>    unorderable items for equality.
> - Flushed out asdict() and astuple().
> - Changed replace() to just call __init__(), and dropped
>    the complex post-create logic.
>

It looks great and I'm excited to get to start using this PEP!


> The only open issues I know of are:
> - Should object comparison require an exact match on the type?
>    https://github.com/ericvsmith/dataclasses/issues/51


I say don't require the type comparison for duck typing purposes.

-Brett


> - Should the replace() function be renamed to something else?
>    https://github.com/ericvsmith/dataclasses/issues/77
>
> Most of the items that were previously discussed on python-dev were
> discussed in detail at https://github.com/ericvsmith/dataclasses. Before
> rehashing an old discussion, please check there first.
>
> Also at https://github.com/ericvsmith/dataclasses is an implementation,
> with tests, that should work with 3.6 and 3.7. The only action item for
> the code is to clean up the implementation of InitVar, but that's
> waiting for PEP 560. Oh, and if PEP 563 is accepted I'll also need to do
> some work.
>
> Feedback is welcomed!
>
> Eric.
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