In general on Stack Overflow, you would have been better editing your original question with an update on your progress.
string.punctuation is definitely a step in the right direction. You've got a few options including:
As to where? If you do it after you create the list, you'll need to apply it to each element individually. But if you split up the your string transformation function calls (split, join) on the return line into their own lines, you could do it earlier. Try performing one action at a time, then printing the result to see if you can spot where else you can remove punctuation without having to iterate.