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Attributes without boilerplate.

Project description

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attrs is an MIT-licensed Python package with class decorators that ease the chores of implementing the most common attribute-related object protocols:

>>> import attr
>>> @attr.s
... class C(object):
...     x = attr.ib(default=42)
...     y = attr.ib(default=attr.Factory(list))
>>> i = C(x=1, y=2)
>>> i
C(x=1, y=2)
>>> i == C(1, 2)
True
>>> i != C(2, 1)
True
>>> attr.asdict(i)
{'y': 2, 'x': 1}
>>> C()
C(x=42, y=[])
>>> C2 = attr.make_class("C2", ["a", "b"])
>>> C2("foo", "bar")
C2(a='foo', b='bar')

(If you don’t like the playful attr.s and attr.ib, you can also use their no-nonsense aliases attr.attributes and attr.attr).

You just specify the attributes to work with and attrs gives you:

  • a nice human-readable __repr__,
  • a complete set of comparison methods,
  • an initializer,
  • and much more

without writing dull boilerplate code again and again.

This gives you the power to use actual classes with actual types in your code instead of confusing tuples or confusingly behaving namedtuples.

So put down that type-less data structures and welcome some class into your life!

attrs’s documentation lives at Read the Docs, the code on GitHub. It’s rigorously tested on Python 2.7, 3.4+, and PyPy.

Release Information

16.0.0 (2016-05-23)

Backward-incompatible changes:

  • Python 3.3 and 2.6 aren’t supported anymore. They may work by chance but any effort to keep them working has ceased.

    The last Python 2.6 release was on October 29, 2013 and isn’t supported by the CPython core team anymore. Major Python packages like Django and Twisted dropped Python 2.6 a while ago already.

    Python 3.3 never had a significant user base and wasn’t part of any distribution’s LTS release.

Changes:

  • __slots__ have arrived! Classes now can automatically be slots-style (and save your precious memory) just by passing slots=True. #35
  • Allow the case of initializing attributes that are set to init=False. This allows for clean initializer parameter lists while being able to initialize attributes to default values. #32
  • attr.asdict can now produce arbitrary mappings instead of Python dicts when provided with a dict_factory argument. #40
  • Multiple performance improvements.

Full changelog.

Credits

attrs is written and maintained by Hynek Schlawack.

The development is kindly supported by Variomedia AG.

A full list of contributors can be found in GitHub’s overview.

It’s the spiritual successor of characteristic and aspires to fix some of it clunkiness and unfortunate decisions. Both were inspired by Twisted’s FancyEqMixin but both are implemented using class decorators because sub-classing is bad for you, m’kay?

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