单例模式的装饰器实现

def singleton(cls):
    __instance = {}

    def wrapper(x):
        if cls in __instance:
            return __instance[cls]
        else:
            __instance[cls] = cls(x)
            return __instance[cls]
    return wrapper


# @singleton
class A:
    def __init__(self,x=0):
        self.x = x

a1 = A(1)
a2 = A(2)
print(a1)
print(a2)