如何将decorators应用于lambdas?

在Python的lambda函数上使用decorator有语法吗?例子:

def simpledecorator(f):
     def new_f():
         print "Using a decorator: "
         f()
     return  new_f

@simpledecorator
def hello():
    print "Hello world!"

>>> hello()
Using a simple decorator:
Hello world!

但当我试着对一只羊羔做同样的尝试时:

@anotherdecorator
f = lambda x: x * 2

我明白了:

  File "<stdin", line 2
    f = lambda x: x * 2
    ^
 SyntaxError: invalid syntax