Parameterized functions of no arguments?

[Rotwang]

Hi all

Sorry if this is a dumb question, I would guess it's answered in an FAQ 
somewhere but I haven't been able to find anything that helps. I'm 
trying to use Tkinter to create a menu whose entries and corresponding 
commands depend on some list x. I want the menu options to be labelled 
by the elements of x, and upon selecting an option k I want my program 
to execute a function f(k). So I tried writing something that 
schematically looked like this:

     def f(k):
         [do something that depends on k]

     menu = Tkinter.Menu(master, tearoff = 0)
     for k in x:
         menu.add_command(label = str(k), command = lambda: f(k))

The trouble is, whenever I open the menu and click on any entry k, 
instead of evaluating f(k) it always evaluates f(x[-1]). I've also tried 
this:

     menu = Tkinter.Menu(master, tearoff = 0)
     for k in x:
         def f():
             [do something that depends on k]
         menu.add_command(label = str(k), command = f)

and it gives me the same problem. Can anybody suggest a way around this?