Although Python doesn't have built-in dictionary comprehensions, you can do something pretty close with little mess or code. Just use .iteritems() to turn your dict into a list, throw it in a generator expression (or list comprehension), and then cast that list back into a dict.

For example, say I have a dictionary of name:email pairs, and I want to create a dictionary of name:is_email_at_a_dot_com pairs: