attrs: Attributes Without Boilerplate

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 methods).

Its main goal is to help you to write concise and correct software without slowing down your code.

For that, it gives you a class decorator and a way to declaratively define the attributes on that class:

>>> 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 tuples or confusingly behaving namedtuples. Which in turn encourages you to write small classes that do one thing well. Never again violate the single responsibility principle just because implementing __init__ et al is a painful drag.

Testimonials

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.

—Glyph Lefkowitz, inventor of Twisted and Software Developer at Rackspace in The One Python Library Everyone Needs

I’m increasingly digging your attr.ocity. Good job!

—Łukasz Langa, prolific CPython core developer and Production Engineer at Facebook

Project Information

attrs is released under the MIT license, its documentation lives at Read the Docs, the code on GitHub, and the latest release on PyPI. It’s rigorously tested on Python 2.7, 3.4+, and PyPy.

Release Information

16.2.0 (2016-09-17)

Changes:

Add attr.astuple() that – similarly to attr.asdict() – returns the instance as a tuple. #77
Converts now work with frozen classes. #76
Instantiation of attrs classes with converters is now significantly faster. #80
Pickling now works with __slots__ classes. #81
attr.assoc() now works with __slots__ classes. #84
The tuple returned by attr.fields() now also allows to access the Attribute instances by name. Yes, we’ve subclassed tuple so you don’t have to! Therefore attr.fields(C).x is equivalent to the deprecated C.x and works with __slots__ classes. #88

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?

Metadata

Release files for attrs 16.2.0

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for attrs 16.2.0
File	Size	Uploaded
attrs-16.2.0.tar.gz	53.1 kB	Sep 17, 2016	Details

Built distribution (wheel)

Table of built distributions (wheels) for attrs 16.2.0
File	Interpreter	ABI	Platform	Reset
attrs-16.2.0-py2.py3-none-any.whl 19.5 kB Sep 17, 2016	Python 2, Python 3	none	any	Details

Total release size: 72.6 kB

Release files / attrs-16.2.0.tar.gz

Download URL	attrs-16.2.0.tar.gz
Size	53.1 kB
Tags	Source
SHA-256 checksum How to use checksums	`136f2ec0f94ec77ff2990830feee965d608cab1e8922370e3abdded383d52001`
BLAKE2b-256 checksum How to use checksums	`6b711682316894ed80b362b9102e7a10997136d8dc1213c36a9f0515c451373a`
Upload date	Sep 17, 2016
Uploaded using Trusted Publishing? What is trusted publishing?	No

Release files / attrs-16.2.0-py2.py3-none-any.whl

Download URL	attrs-16.2.0-py2.py3-none-any.whl
Size	19.5 kB
Tags	Python 2 Python 3
SHA-256 checksum How to use checksums	`ce9d6cac4705e5aeaca02d3ff72f0006bf9b0a2f29635ae8dab8262e296f6442`
BLAKE2b-256 checksum How to use checksums	`41c5b7ab0d97bb20cec1ca4bb1f0a418c5f50022b6624e6417e997b2e1c034d5`
Upload date	Sep 17, 2016
Uploaded using Trusted Publishing? What is trusted publishing?	No