characteristic: Say ‘yes’ to types but ‘no’ to typing!

Release v14.1.0 (What’s new?).

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

You just specify the attributes to work with and characteristic gives you any or all of:

  • a nice human-readable __repr__,
  • a complete set of comparison methods,
  • immutability for attributes,
  • and a kwargs-based initializer (that cooperates with your existing one and optionally even checks the types of the arguments)

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!

characteristic’s documentation lives at Read the Docs, the code on GitHub. It’s rigorously tested on Python 2.6, 2.7, 3.3+, and PyPy.

Teaser

>>> from characteristic import Attribute, attributes
>>> @attributes(["a", "b"])
... class AClass(object):
...     pass
>>> @attributes(["a", Attribute("b", default_value="abc", instance_of=str)])
... class AnotherClass(object):
...     pass
>>> obj1 = AClass(a=1, b="abc")
>>> obj2 = AnotherClass(a=1, b="abc")
>>> obj3 = AnotherClass(a=1)
>>> AnotherClass(a=1, b=42)
Traceback (most recent call last):
 ...
TypeError: Attribute 'b' must be an instance of 'str'.
>>> print obj1, obj2, obj3
<AClass(a=1, b='abc')> <AnotherClass(a=1, b='abc')> <AnotherClass(a=1, b='abc')>
>>> obj1 == obj2
False
>>> obj2 == obj3
True

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