Adding spaces to digits

[rob101]

There are a few different ways to do this and your code can be made much more succinct.

This (for example) removes the hyphens and reverses each 'token'. The resulting tokens are replaced, within the same list object.

ccn = "2323-2005-7766-3554"
ccn_lst = ccn.split("-")

for index, token in enumerate(ccn_lst):
    ccn_lst[index] = token[::-1]

Have a look into string slicing to see how this works and to complete the rest of your project.

to add: you could also look into the third perimeter of the range() function, which is commonly called a 'step': range(start, stop, step).