Singleton

Cách 1

class Singleton(object):
    _instance = {}

    def __new__(cls, *args, **kwargs):
        if not isinstance(cls._instance, cls):
            cls._instance = super().__new__(cls)
        return cls._instance


class MyClass(Singleton):
    pass

Cách 2

class Singleton(type):
    _instances = {}

    def __call__(cls, *args, **kwargs):
        if cls not in cls._instances:
            cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
        return cls._instances[cls]


class MyClass(metaclass=Singleton):
    pass