[python] Python function overloading

You can use "roll-your-own" solution for function overloading. This one is copied from Guido van Rossum's article about multimethods (because there is little difference between multimethods and overloading in Python):

registry = {}

class MultiMethod(object):
    def __init__(self, name):
        self.name = name
        self.typemap = {}
    def __call__(self, *args):
        types = tuple(arg.__class__ for arg in args) # a generator expression!
        function = self.typemap.get(types)
        if function is None:
            raise TypeError("no match")
        return function(*args)
    def register(self, types, function):
        if types in self.typemap:
            raise TypeError("duplicate registration")
        self.typemap[types] = function


def multimethod(*types):
    def register(function):
        name = function.__name__
        mm = registry.get(name)
        if mm is None:
            mm = registry[name] = MultiMethod(name)
        mm.register(types, function)
        return mm
    return register

The usage would be

from multimethods import multimethod
import unittest

# 'overload' makes more sense in this case
overload = multimethod

class Sprite(object):
    pass

class Point(object):
    pass

class Curve(object):
    pass

@overload(Sprite, Point, Direction, int)
def add_bullet(sprite, start, direction, speed):
    # ...

@overload(Sprite, Point, Point, int, int)
def add_bullet(sprite, start, headto, speed, acceleration):
    # ...

@overload(Sprite, str)
def add_bullet(sprite, script):
    # ...

@overload(Sprite, Curve, speed)
def add_bullet(sprite, curve, speed):
    # ...

Most restrictive limitations at the moment are:

  • methods are not supported, only functions that are not class members;
  • inheritance is not handled;
  • kwargs are not supported;
  • registering new functions should be done at import time thing is not thread-safe

Examples related to python

programming a servo thru a barometer Is there a way to view two blocks of code from the same file simultaneously in Sublime Text? python variable NameError Why my regexp for hyphenated words doesn't work? Comparing a variable with a string python not working when redirecting from bash script is it possible to add colors to python output? Get Public URL for File - Google Cloud Storage - App Engine (Python) Real time face detection OpenCV, Python xlrd.biffh.XLRDError: Excel xlsx file; not supported Could not load dynamic library 'cudart64_101.dll' on tensorflow CPU-only installation

Examples related to class

String method cannot be found in a main class method Class constructor type in typescript? ReactJS - Call One Component Method From Another Component How do I declare a model class in my Angular 2 component using TypeScript? When to use Interface and Model in TypeScript / Angular Swift Error: Editor placeholder in source file Declaring static constants in ES6 classes? Creating a static class with no instances In R, dealing with Error: ggplot2 doesn't know how to deal with data of class numeric Static vs class functions/variables in Swift classes?

Examples related to oop

How to implement a simple scenario the OO way When to use 'raise NotImplementedError'? PHP: cannot declare class because the name is already in use Python class input argument Call an overridden method from super class in typescript Typescript: How to extend two classes? What's the difference between abstraction and encapsulation? An object reference is required to access a non-static member Java Multiple Inheritance Why not inherit from List<T>?

Examples related to overloading

What is the difference between dynamic and static polymorphism in Java? TypeScript function overloading Constructor overload in TypeScript What is the difference between method overloading and overriding? Differentiate between function overloading and function overriding How do I use method overloading in Python? How can I create a Java method that accepts a variable number of arguments? Python function overloading PHP function overloading What is function overloading and overriding in php?

Examples related to multiple-dispatch

Python function overloading