how to get the location of a letter in a string in python code example

Example 1: get the string after a character in php

$data = "123_String";    
$whatIWant = substr($data, strpos($data, "_") + 1);    
echo $whatIWant;

Example 2: python how to get the last element in a list

some_list = [1, 2, 3]
some_list[-1]
print(some_list)
#Output = 3