Python list comprehension - access last created element?

Question

Is it possible to access the previous element generated in a list comprehension.

I am working on some toy encryption stuff. Given the key as an arbitrarily large in

Answer 1

You could have done this using reduce(). It's not list comprehension, but it's the functional style approach:

cipher = []
def f(previous, element):
    previous = element ^ previous ^ key
    cipher.append(previous)
    return previous
reduce(f, message, initialization_value)

It isn't any prettier than the plain loop in this case though.