[New-bugs-announce] [issue32977] added acts_like decorator to dataclasses module

[Aaron Christianson]

New submission from Aaron Christianson <ninjaaron at gmail.com>:

I'm always writting these wrapper classes where I want to selectively want to expose the interface of some of the methods of certain attributes to co the containing object. This can mean I spend a lot of time implementing wrapper methods. That's no good. I wrote a class decorator to make this easy, and I realized it's a perfect complement to the new dataclasses module, though it can also be used with normal classes. I figured I'd check if you're interested in that. The interface looks like this:

>>> from dataclasses import dataclass, acts_like
>>> @acts_like('weight', ['__add__'])
... @acts_like('still_fresh', ['__bool__'])
... @dataclass
... class Spam:
...     weight: int
...     still_fresh: bool
>>> s = Spam(42, False)
>>> s + 3
45
>>> if not s:
...     print('the spam is bad')
the spam is bad

It's a handy way to build objects with composition, but still get some of the benefits of inheritance in a *selective* and *explicite* way.

Here's the code: https://github.com/ninjaaron/cpython/blob/acts_like/Lib/dataclasses.py#L978

May require some addtional twiddling to make it work with frozen dataclasses, but I don't think it should be a problem.

----------
components: Library (Lib)
messages: 313096
nosy: eric.smith, ninjaaron
priority: normal
severity: normal
status: open
title: added acts_like decorator to dataclasses module
type: enhancement
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue32977>
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