lambda question

[David Bear]

I was hoping to use lambda to create some quick string transforming 
functions.  So I did :

name = "a title"
title = lambda s: "<title> % </title>" % s
print title(name)
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "<stdin>", line 1, in <lambda>

I don't understand this.  Is lambda not a good way to do this?  I was hoping 
to avoid function overhead by creating some anonymous functions, but I 
guess I don't understand how to use them.. any comments?