how to find the position of the last letter of a string in python code example

Example 1: last character of string in python

a = '123456789'

#to get last char, acess index -1
print(a[-1])

#this works the same as:
print(a[len(a)-1])

#instead of 1, subtract n to get string's nth char from last
#let n = 4
print(a[-4])

#result:
9
9
6

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"