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: ['D', '2831', '3665', '3445', 'o', '5757', '8217', '2129', 'W', '8119', 'B', '4345', '3239', '6871', '1593', '5415']

4, 2831, 3665, 3445, 15, 5757, 8217, 2129, 23, 8119, 2, 4345, 3239, 6871, 1593, 5415