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Retrieve all classes derived from a class and sort them by a given priority and order, making it easy to draw up and use plugin-like classes.

Project description

Makes classes sortable by precedence and priority. The order of precedence of classes and their priority is defined de-centrally and at runtime.

Copyright 2016, 2017, 2018 Odin Kroeger

Use case

sortableclasses makes classes sortable. This is useful if all you want to do is take some input, apply a set of transformations, and output the result (i.e., are writing what on UNIX-ish systems is called a ‘filter’). Of course, you may just write, e.g., return t1(t2(t3(...(tn(input)))))) but the more transformations you need to add, the harder this is to maintain. sortableclasses allows you to turn the transformations into classes, assign each of them a priority (or a list of predecessors and successors) and then sort them using sort sorted.

>>> import sortableclasses
>>> import abc
>>> import functools
>>> class Transform(sortableclasses.Pluggable):
...     @staticmethod
...     @abc.abstractmethod
...     def transform(input):
...         pass
>>> class MakeContent(Transform):
...     @staticmethod
...     def transform(input):
...         if input == ':-(':
...             return ':-|'
...         return input
>>> class MakeHappy(Transform):
...     successorof = (MakeContent,)
...     @staticmethod
...     def transform(input):
...         if input == ':-|':
...             return ':-)'
...         return input
>>> class MakeVeryHappy(Transform):
...     successorof = (MakeHappy,)
...     @staticmethod
...     def transform(input):
...         if input == ':-)':
...             return ':-D'
...         return input
>>> transforms = sorted(Transform.getderived())
>>> transforms
[<class 'MakeContent'>, <class 'MakeHappy'>, <class 'MakeVeryHappy'>]
>>> input = ':-('
>>> functools.reduce(lambda k, s: s.transform(k), transforms, input)


You use sortableclasses at your own risk. You have been warned.

sortableclasses works only in Python 3.

Clone the repository and run install.


See <> for reference.

You can also view the inline documentation, by:

pydoc sortableclasses


If there’s something wrong with sortableclasses, please open an issue at:


This programme is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

This programme is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program. If not, see <>.

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