This function allows an user to reverse a sub-string within a string or a sub-list within a list. I don't know why but this might be useful to someone.

reverse_list_substring.py

#!/usr/bin/env python3

# l = Full list or string to be reversed. 
# start = Index where the sub-string to be reversed starts
# end = Index where the sub-string to be reversed ends

def rev_sub(l, start, end):
  return l[0:start]+l[start:end+1][::-1]+l[end+1:]