Specify negative indexes if you want to start the search from the end of the list:
This example returns the items from index -4 (included) to index -1 (excluded)
thislist = ["apple", "banana", "cherry", "orange", "kiwi", "melon", "mango"]
print(thislist[-4:-1])
Change the second item:
thislist = ["apple", "banana", "cherry"]
thislist[1] = "blackcurrant"
print(thislist)