attrs/README.rst

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=====================================
attrs: Attributes Without Boilerplate
=====================================
.. image:: https://readthedocs.org/projects/attrs/badge/?version=stable
:target: http://attrs.readthedocs.io/en/stable/?badge=stable
:alt: Documentation Status
.. image:: https://travis-ci.org/hynek/attrs.svg?branch=master
:target: https://travis-ci.org/hynek/attrs
:alt: CI status
.. image:: https://codecov.io/github/hynek/attrs/branch/master/graph/badge.svg
:target: https://codecov.io/github/hynek/attrs
:alt: Test Coverage
.. 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 <http://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 C(object):
... x = attr.ib(default=42)
... y = attr.ib(default=attr.Factory(list))
...
... def hard_math(self, z):
... return self.x * self.y * z
>>> i = C(x=1, y=2)
>>> i
C(x=1, y=2)
>>> i.hard_math(3)
6
>>> 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')
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,
- an initializer,
- and much more,
*without* writing dull boilerplate code again and again and *without* runtime performance penalties.
This gives you the power to use actual classes with actual types in your code instead of confusing ``tuple``\ s or confusingly behaving ``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
============
Im 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 Ive see it used in.
-- Glyph Lefkowitz, inventor of Twisted and Software Developer at Rackspace in `The One Python Library Everyone Needs <https://glyph.twistedmatrix.com/2016/08/attrs.html>`_
I'm increasingly digging your attr.ocity. Good job!
-- Łukasz Langa, prolific CPython core developer and Production Engineer at Facebook
.. -end-
.. -project-information-
Project Information
===================
``attrs`` is released under the `MIT <http://choosealicense.com/licenses/mit/>`_ license,
its documentation lives at `Read the Docs <https://attrs.readthedocs.io/>`_,
the code on `GitHub <https://github.com/hynek/attrs>`_,
and the latest release on `PyPI <https://pypi.org/project/attrs/>`_.
Its rigorously tested on Python 2.7, 3.4+, and PyPy.