Definition: In this task, you are given an input list A. You need to convert all the alphabets in the list with a number representing their position in the English alphabet. E.g., replace A by 1, B by 2, a by 1, b by 2, and so on.
Input: ['t', '6721', 'h', '1791', 'd', '6335', '6641', '3471', 'u', 'j', '2203', 'G', '3873', 'L', 'Y', '1545', 'q', '8067', '8141']

20, 6721, 8, 1791, 4, 6335, 6641, 3471, 21, 10, 2203, 7, 3873, 12, 25, 1545, 17, 8067, 8141