理解调用@log与@log()效果一致的原因

django 框架中自定义标签在注册时使用装饰器的过程中使用@register.simple_tag与@register.simple_tag()结果一致的解释

'''
理解调用@log与@log()效果一致的原因
'''
def log(func=None):
    def wraper(fun):
        def inner(*args,**kwargs):
            print('do something before')
            res = fun(*args,**kwargs)
            print('do something after')
            return res
        return inner

    if func is None:
        return wraper
    elif callable(func):
        return wraper(func)

@log
def my_func():
    print('i am my_func')

if __name__ == '__main__':
    my_func()

#my_func = log(func)
#my_func = log()(func)