Automate the boring stuff with Python: Comma Code

Question

Currently working my way through this beginners book and have completed one of the practice projects \'Comma Code\' which asks the user to construct a program which:

Answer 1

Others have given great one-liner solutions, but a good way to improve your actual implementation - and fix the fact that it does not work when elements are repeated - is to use enumerate in the for loop to keep track of the index, rather than using index which always finds the first occurrence of the target.

for counter, element in enumerate(list):
    new_string = new_string + str(element)
    if counter == (len(list)-2):
        ...