Dispatcher pattern implementation and use cases: polymorphism, router.

dispatcher.py

from abc import ABC, abstractmethod


class Dispatcher(ABC):
    @abstractmethod
    def _get_key():
        raise NotImplementedError

    @classmethod
    def register(cls, key):
        def wrapper(func):
            cls._mapping[key] = func
        return wrapper

    @classmethod
    def run(cls, *args):
        key = cls._get_key(args)
        if key not in cls._mapping:
            raise ValueError
        return cls._mapping[key](*args)



class Add(Dispatcher):
    _mapping = {}
    
    @staticmethod
    def _get_key(args):
        return type(args[0])


class Get(Dispatcher):
    _mapping = {}
    
    @staticmethod
    def _get_key(args):
        return args[0]


@Add.register(int)
def _(*numbers):
    return sum(numbers)


@Add.register(str)
def _(*words):
    return ' '.join(words)


@Get.register('/')
def _(url, *params):
    return 200, 'Welcome to the candy shop!'


@Get.register('/candies')
def _(url, *params):
    colors = ['calisson', 'nougat', 'macaron']
    if not params:
        return 200, {'candies': colors}
    idx = params[0]
    if idx in range(len(colors)):
        return 200, {'candy': colors[idx]}
     return 404, f'Candy `{idx}` not found.'


add = Add.run
assert add(1, 2, 3) == 6
assert add('hello', 'world') == 'hello world'


get = Get.run
assert get('/') == 200, 'Welcome to the candy shop!'
assert get('/colors') == 200, {'candies': ['calisson', 'nougat', 'macaron']}
assert get('/colors', 0) == 200, {'candy': 'calisson'}
assert get('/colors', 4) == 404, 'Candy `4` not found.'