multipledispatch 1.0.0

Example

>>> 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

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*