def square(n):
    return n * n

numbers = [1, 3, 5, 7]

squares1 = [square(n) for n in numbers]     # list comprehension

squares2a = map(square, numbers)            # functional form

squares2b = map(lambda x: x*x, numbers)     # functional form with `lambda`

squares3 = [n * n for n in numbers]         # no need for a function,
                                            # anonymous or otherwise

isquares1 = (n * n for n in numbers)        # iterator, lazy

import itertools
isquares2 = itertools.imap(square, numbers) # iterator, lazy