Proper deletion of selected items during map iteration in for loop

[Charles Hixson]

What is the proper way to delete selected items during iteration of a 
map?  What I want to do is:

for (k, v) in m.items():
    if f(k):
       #  do some processing of v and save result elsewhere
       del m[k]

But this gives (as should be expected):
         RuntimeError: dictionary changed size during iteration
In the past I've accumulated the keys to be deleted in a separate list, 
but this time there are likely to be a large number of them, so is there 
some better way?

-- 
Charles Hixson