lambda expression

[Alex]

> I'd like to write something like
> 
> u=filter(lambda x: k in d[x],u),
> 
> where d is a dictionary, u is (of course) a list and k a variable declared
> in the function where the lines is in. But i does not work, it seems, k ist
> not known inside of the lambda expression.
> Any suggestions? Any help?

The usual trick is to use default arguments.  E.g.

u=filter(lambda x, k=k: k in d[x],u)

Alex.