import functools

def log(test=""):
    def decorator(func):
        @functools.wraps(func)
        def wrappers(*args,**kw):
            print("%s begin call : %s" % (test,func.__name__))
            result =  func(*args,**kw)
            print("%s end call :  %s "% (test,func.__name__))
            return result
        return wrappers
    return decorator

@log('execute')
def now():
    print('2016-01-16')
now()

print("==============")

@log()
def now():
    print('2016-01-16')
now()

结果是：

execute begin call : now
2016-01-16
execute end call :  now
==============
 begin call : now
2016-01-16
 end call :  now