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', 'H', 'O', 'l', '1719', '2361', 'Q', '5331', 'n', 'T', '5255', 'N', 'a', '5815', '8555', '6497', 'Z', '9229', '2403', '7515']

20, 8, 15, 12, 1719, 2361, 17, 5331, 14, 20, 5255, 14, 1, 5815, 8555, 6497, 26, 9229, 2403, 7515