.. image:: https://www.attrs.org/en/latest/_static/attrs_logo.png
:alt: attrs Logo
======================================
attrs: Classes Without Boilerplate
.. image:: https://readthedocs.org/projects/attrs/badge/?version=stable
:target: https://www.attrs.org/en/stable/?badge=stable
:alt: Documentation Status
.. image:: https://attrs.visualstudio.com/attrs/_apis/build/status/python-attrs.attrs?branchName=master
:target: https://attrs.visualstudio.com/attrs/_build/latest?definitionId=1&branchName=master
:alt: CI Status
.. image:: https://codecov.io/github/python-attrs/attrs/branch/master/graph/badge.svg
:target: https://codecov.io/github/python-attrs/attrs
:alt: Test Coverage
.. image:: https://img.shields.io/badge/code%20style-black-000000.svg
:target: https://github.com/psf/black
:alt: Code style: black
.. teaser-begin
attrs is the Python package that will bring back the joy of writing classes by relieving you from the drudgery of implementing object protocols (aka dunder <https://nedbatchelder.com/blog/200605/dunder.html>_ methods).
Its main goal is to help you to write concise and correct software without slowing down your code.
.. -spiel-end-
For that, it gives you a class decorator and a way to declaratively define the attributes on that class:
.. -code-begin-
.. code-block:: pycon
import attr
@attr.s
... class SomeClass(object):
... a_number = attr.ib(default=42)
... list_of_numbers = attr.ib(factory=list)
...
... def hard_math(self, another_number):
... return self.a_number + sum(self.list_of_numbers) * another_number
sc = SomeClass(1, [1, 2, 3])
sc
SomeClass(a_number=1, list_of_numbers=[1, 2, 3])
sc.hard_math(3)
19
sc == SomeClass(1, [1, 2, 3])
True
sc != SomeClass(2, [3, 2, 1])
True
attr.asdict(sc)
{'a_number': 1, 'list_of_numbers': [1, 2, 3]}
SomeClass()
SomeClass(a_number=42, list_of_numbers=[])
C = attr.make_class("C", ["a", "b"])
C("foo", "bar")
C(a='foo', b='bar')
After declaring your attributes attrs gives you:
- a concise and explicit overview of the class's attributes,
- a nice human-readable
__repr__, - a complete set of comparison methods (equality and ordering),
- an initializer,
- and much more,
without writing dull boilerplate code again and again and without runtime performance penalties.
On Python 3.6 and later, you can often even drop the calls to attr.ib() by using type annotations <https://www.attrs.org/en/latest/types.html>_.
This gives you the power to use actual classes with actual types in your code instead of confusing tuple\ s or confusingly behaving <https://www.attrs.org/en/stable/why.html#namedtuples>_ namedtuple\ s.
Which in turn encourages you to write small classes that do one thing well <https://www.destroyallsoftware.com/talks/boundaries>.
Never again violate the single responsibility principle <https://en.wikipedia.org/wiki/Single_responsibility_principle> just because implementing __init__ et al is a painful drag.
.. -testimonials-
Testimonials
Amber Hawkie Brown, Twisted Release Manager and Computer Owl:
Writing a fully-functional class using attrs takes me less time than writing this testimonial.
Glyph Lefkowitz, creator of Twisted <https://twistedmatrix.com/>, Automat <https://pypi.org/project/Automat/>, and other open source software, in The One Python Library Everyone Needs <https://glyph.twistedmatrix.com/2016/08/attrs.html>_:
I’m looking forward to is being able to program in Python-with-attrs everywhere.
It exerts a subtle, but positive, design influence in all the codebases I’ve see it used in.
Kenneth Reitz, creator of Requests <https://github.com/psf/requests>_ (on paper no less <https://twitter.com/hynek/status/866817877650751488>_!):
attrs—classes for humans. I like it.
Łukasz Langa, creator of Black <https://github.com/psf/black>_, prolific Python core developer, and release manager for Python 3.8 and 3.9:
I'm increasingly digging your attr.ocity. Good job!
.. -end-
.. -project-information-
Getting Help
Please use the python-attrs tag on StackOverflow <https://stackoverflow.com/questions/tagged/python-attrs>_ to get help.
Answering questions of your fellow developers is also great way to help the project!
Project Information
attrs is released under the MIT <https://choosealicense.com/licenses/mit/>_ license,
its documentation lives at Read the Docs <https://www.attrs.org/>,
the code on GitHub <https://github.com/python-attrs/attrs>,
and the latest release on PyPI <https://pypi.org/project/attrs/>_.
It’s rigorously tested on Python 2.7, 3.5+, and PyPy.
We collect information on third-party extensions in our wiki <https://github.com/python-attrs/attrs/wiki/Extensions-to-attrs>_.
Feel free to browse and add your own!
If you'd like to contribute to attrs you're most welcome and we've written a little guide <https://www.attrs.org/en/latest/contributing.html>_ to get you started!