如何确定缺少哪个Python关键字参数？

Question

当忘记将某些参数传递给函数时,Python给出了唯一有用的消息"myfunction()接受X参数(给定Y)".有没有办法弄清楚缺少的参数的名称,并告诉用户？就像是:

try:
    #begin blackbox
    def f(x,y):
        return x*y

    f(x=1)
    #end blackbox
except Exception as e:
    #figure out the missing keyword argument is called "y" and tell the user so

假设开始blackbox和end blackbox之间的代码对于异常处理程序是未知的.

编辑:正如我在下面指出的那样,Python 3已经内置了这个功能.让我扩展一下这个问题,是否有一种(可能是丑陋和hacky)方法在Python 2.x中执行此操作？

Answer 1

except TypeError as e:
   import inspect
   got_args = int(re.search("\d+.*(\d+)",str(e)).groups()[0])
   print "missing args:",inspect.getargspec(f).args[got_args:]

更好的方法是装饰器

def arg_decorator(fn):
   def func(*args,**kwargs):
       try: 
           return fn(*args,**kwargs)
       except TypeError:
           arg_spec = inspect.getargspec(fn)
           missing_named = [a for a in arg_spec.args if a not in kwargs]
           if arg_spec.defaults:
                    missing_args = missing_named[len(args): -len(arg_spec.defaults) ]
           else:
                    missing_args = missing_named[len(args):]
           print "Missing:",missing_args
   return func

@arg_decorator
def fn1(x,y,z):                      
      pass

def fn2(x,y):
    pass

arged_fn2 = arg_decorator(fn2)

fn1(5,y=2)
arged_fn2(x=1)