Python两种方式实现单例模式

装饰器模式实现单例

from functools import wraps


def singleton(cls):
    instances = {}

    @wraps(cls)
    def get_instance(*args, **kwargs):
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]

    return get_instance

@singleton
class Second:
    def __init__(self, config):
        self.config = config

    def print_config(self):
        print(self.config)

通过拦截类创建的是模式实现单例

class SingletonCls(type):
    instance = {}

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


class Base(metaclass=SingletonCls):
    def __init__(self, config):
        self.config = config

    def print_config(self):
        print(self.config)

测试结果

if __name__ == '__main__':
    b = Base("145")
    b.print_config()
    c = Base("234")
    c.print_config()

    print("---装饰器实现---")

    d = Second("k8s")
    d.print_config()
    e = Second("k3s")
    e.print_config()