occurrence of character in string python code example

Example 1: python search first occurrence in string

s = "the dude is a cool dude"
s.find('dude') # returns 4 - the first index of the first match in the string

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"