last occurrence of a character in a list python code example

Example 1: python last index of item in list

def list_rindex(li, x):
    for i in reversed(range(len(li))):
        if li[i] == x:
            return i
    raise ValueError("{} is not in list".format(x))

Example 2: how to find the last occurrence of a character in a string in python

original_string = "sentence one. sentence two. sentence three"

last_char_index = original_string.rfind(".")
new_string = original_string[:last_char_index] + "," + original_string
print(new_string)
"sentence one. sententce two, sentence three"