def log(text):
    def real_decorator(func):
        @functools.wraps(func)
        def wrapper(*args, **kw):
            if isinstance(text,str): display=text
            else:display=''
            print('begin call',display)
            func()
            print('end call')
        return wrapper
    if isinstance(text,str):
        return real_decorator
    else:
        return real_decorator(text)

@log('ext')
def f():
    print('call f()')

@log
def f1():
    print('call f1()')

f()
f1()

output

begin call ext
call f()
end call
begin call 
call f1()
end call

不知道是不是标准写法。。。总之可以work。。。