Multiple Dispatch

A relatively sane approach to multiple dispatch in Python.

This implementation of multiple dispatch is efficient, mostly complete,
performs static analysis to avoid conflicts, and provides optional namespace
support. It looks good too.

See the documentation at https://multiple-dispatch.readthedocs.io/

Example

.. code-block:: python

from multipledispatch import dispatch

@dispatch(int, int)
... def add(x, y):
... return x + y

@dispatch(object, object)
... def add(x, y):
... return "%s + %s" % (x, y)

add(1, 2)
3

add(1, 'hello')
'1 + hello'

What this does

Dispatches on all non-keyword arguments
Supports inheritance
Supports instance methods
Supports union types, e.g. (int, float)
Supports builtin abstract classes, e.g. Iterator, Number, ...
Caches for fast repeated lookup
Identifies possible ambiguities at function definition time
Provides hints to resolve ambiguities when they occur
Supports namespaces with optional keyword arguments
Supports variadic dispatch

What this doesn't do

Diagonal dispatch

.. code-block:: python

a = arbitrary_type()
@dispatch(a, a)
def are_same_type(x, y):
return True

Efficient update: The addition of a new signature requires a full resolve of
the whole function. This becomes troublesome after you get to a few hundred
type signatures.

Installation and Dependencies

multipledispatch is on the Python Package Index (PyPI):

::

pip install multipledispatch

It is Pure-Python and depends only on the standard library.
It is a light weight dependency.

License

New BSD. See License file_.

Links

Five-minute Multimethods in Python by Guido_
multimethods package on PyPI_
singledispatch in Python 3.4's functools_
Clojure Protocols_
Julia methods docs_
Karpinksi notebook: *The Design Impact of Multiple Dispatch*_
Wikipedia article_
PEP 3124 - *Overloading, Generic Functions, Interfaces, and Adaptation*_

.. _Five-minute Multimethods in Python by Guido:
http://www.artima.com/weblogs/viewpost.jsp?thread=101605
.. _multimethods package on PyPI:
https://pypi.python.org/pypi/multimethods
.. _singledispatch in Python 3.4's functools:
http://docs.python.org/3.4/library/functools.html#functools.singledispatch
.. _Clojure Protocols:
http://clojure.org/protocols
.. _Julia methods docs:
https://docs.julialang.org/en/v1/manual/methods/
.. _Karpinksi notebook: *The Design Impact of Multiple Dispatch*:
http://nbviewer.ipython.org/gist/StefanKarpinski/b8fe9dbb36c1427b9f22
.. _Wikipedia article:
http://en.wikipedia.org/wiki/Multiple_dispatch
.. _PEP 3124 - *Overloading, Generic Functions, Interfaces, and Adaptation*:
http://legacy.python.org/dev/peps/pep-3124/

.. |Build Status| image:: https://travis-ci.org/mrocklin/multipledispatch.svg
:target: https://travis-ci.org/mrocklin/multipledispatch
.. |Version Status| image:: https://pypip.in/v/multipledispatch/badge.svg
:target: https://img.shields.io/pypi/v/multipledispatch.svg
.. |Coverage Status| image:: https://coveralls.io/repos/mrocklin/multipledispatch/badge.svg
:target: https://coveralls.io/r/mrocklin/multipledispatch
.. _License file: https://github.com/mrocklin/multipledispatch/blob/master/LICENSE.txt

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multipledispatch

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