https://github.com/ikalnytskyi/singledispatchmethod

Backport of 'functools.singledispatchmethod' from Python 3.8 to Python 2.7 - 3.7.
https://github.com/ikalnytskyi/singledispatchmethod

backport python singledispatch

Last synced: 14 days ago
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Backport of 'functools.singledispatchmethod' from Python 3.8 to Python 2.7 - 3.7.

• Host: GitHub
• URL: https://github.com/ikalnytskyi/singledispatchmethod
• Owner: ikalnytskyi
• License: other
• Created: 2019-08-11T14:18:07.000Z (about 5 years ago)
• Default Branch: master
• Last Pushed: 2019-08-12T07:15:12.000Z (about 5 years ago)
• Last Synced: 2024-10-04T15:37:48.055Z (about 1 month ago)
• Topics: backport, python, singledispatch
• Language: Python
• Homepage:
• Size: 6.84 KB
• Stars: 15
• Watchers: 3
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README.rst
  • License: LICENSE

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README

        
singledispatchmethod

====================

Backport of ``@functools.singledispatchmethod`` decorator [1]_ from

Python 3.8 to Python 2.7-3.7. These are merely ~30 lines of code, but

why bother yourself with copypasta?

.. code:: bash

   $ pip install singledispatchmethod

The decorator transforms a method into a single-dispatch [2]_ generic

function [3]_. Note that since the dispatch happens on the type of the

first non-self or non-cls argument, you have to create your function

accordingly:

.. code:: python

    from singledispatchmethod import singledispatchmethod

    class Negator:

        @singledispatchmethod

        def neg(self, arg):

            raise NotImplementedError("Cannot negate a")

        @neg.register

        def _(self, arg: int):

            return -arg

        @neg.register

        def _(self, arg: bool):

            return not arg

``@singledispatchmethod`` supports nesting with other decorators such as

``@classmethod``. However, in order to expose ``dispatcher.register``,

``@singledispatchmethod`` must be the *outer most* decorator. Here is

the ``Negator`` class with the ``neg`` methods being class bound:

.. code:: python

    from singledispatchmethod import singledispatchmethod

    class Negator:

        @singledispatchmethod

        @classmethod

        def neg(cls, arg):

            raise NotImplementedError("Cannot negate a")

        @neg.register

        @classmethod

        def _(cls, arg: int):

            return -arg

        @neg.register

        @classmethod

        def _(cls, arg: bool):

            return not arg

The same pattern can be used for other similar decorators, such as

``@staticmethod`` or ``@abstractmethod``. Please note, since

``@singledispatchmethod`` decorator is based on

``@functools.singledispatch``, type annotations are supported by

``dispatcher.register`` only since Python 3.7.

.. [1] https://docs.python.org/3.8/library/functools.html#functools.singledispatchmethod

.. [2] https://docs.python.org/3.8/glossary.html#term-single-dispatch

.. [3] https://docs.python.org/3.8/glossary.html#term-generic-function