Python 设计模式-单例模式

Python中有多种实现单例模式的方式，以下是其中的几种：

1. 基础单例模式

class Singleton(object):
    __instance = None
 
    def __new__(cls, *args, **kwargs):
        if not cls.__instance:
            cls.__instance = object.__new__(cls)
        return cls.__instance

2. 使用装饰器实现单例模式

def singleton(cls):
    instances = {}
 
    def get_instance(*args, **kwargs):
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]
 
    return get_instance
 
 
@singleton
class MyClass:
    pass

3. 使用元类实现单例模式

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