# def dec1(fn):
#     def sayspam(*args):
#         print("dec1")
#         fn(*args)
#     return sayspam

# def dec2(fn):
#     def sayspam(*args):
#         print("dec2")
#         fn(*args)
#     return sayspam

# @dec2
# @dec1
# def useful(a,b):
#     print(a*b)

# if __name__ == "__main__":
#   useful(2,5)

#程序退出时执行
# def onexit(f):
#     import atexit
#     atexit.register(f)
#     return f


# @onexit
# def func():
#     print("onexit")

#单例
def singleton(cls):
    instances = {}
    def getinstance():
        if cls not in instances:
            instances[cls] = cls()
        return instances[cls]
    return getinstance

@singleton
class MyClass:
    def __init__(self):
        print(self)


#添加参数
def attrs(**kwds):
    def decorate(f):
        for k in kwds:
            setattr(f, k, kwds[k])
        return f

    return decorate


@attrs(versionadded="2.2",
       author="Guido van Rossum")
def mymethod(f):
    print(getattr(mymethod,'versionadded',0))
    print(getattr(mymethod,'author',0))
    print(f)

if __name__ == "__main__":
    # x = MyClass()
    # y = MyClass()
    mymethod(2)