Multiple Dispatch 2

This is a fork from `mroklin's multipledispatch<https://github.com/mrocklin/multipledispatch>`_, which is designed to fully support python 3's type annotation.

And it only supports python 3.3+.

Example

>>> from multipledispatch2 import dispatch

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

>>> @dispatch
... 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

What this doesn't do

• Vararg dispatch

import typing

@dispatch
def add(*args: typing.Iterable[int]):
    ...

• Diagonal dispatch

a = arbitrary_type()
@dispatch
def are_same_type(x: a, y: a) -> bool:
    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. It can be mitigated by halting and restarting ordering see (halt_ordering and restart_ordering functions for more information.)

Installation and Dependencies

multipledispatch2 is on the Python Package Index (PyPI):

pip install multipledispatch2

or

easy_install multipledispatch2

multipledispatch2 is only supports Python 3.3+. It is pure Python and requires no dependencies beyond the standard library.

It is, in short, a light weight dependency.

License

New BSD. See License.

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*
• PEP 0484 - *Type Hints*