Dickens

Additional Python decorators implementing the descriptor interface.

Use cases

Like the built-in decorator, property, these classes are initialized by and wrap a function, generally within the context of a class, in order to modify its behavior.

cached property

This decorator functions much like a read-only property, with the difference that, upon access, it records its result in the instance's object data dictionary, which reference takes precedence in look-ups, thereby replacing itself for that object:

from descriptors import cachedproperty

@cachedproperty
def circumference(self):
    return 2 * math.pi * self.radius

class property

A read-only property for class methods:

from descriptors import classproperty

@classproperty
def badpi(cls):
    return 22 / 7

cached class property

A class property, which caches its result in the data dictionary of the class from which it was invoked, (under another name, so as not to interfere with inheritance of the property):

from descriptors import cachedclassproperty

@cachedclassproperty
def badpi(cls):
    return 22 / 7

class-only method

A class method that cannot be accessed as an instance method:

from descriptors import classonlymethod

@classonlymethod
def circumference(cls, radius):
    return 2 * cls.pi * radius

The class-only method may be overshadowed by instance data set under the same name.

Otherwise, instance access raises AttributeError (and such that it is forwarded to and may be handled by the instance's __getattr__).

Installation

Dickens is a Python distribution, which may be installed via easy_install or pip, e.g.:

pip install Dickens

...or, from source:

python setup.py install