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: ['B', '173', '637', '6477', 't', '3977', '2085', 'n', 'r', 'L', '8397', '5857', 'u', 'U', 'b', 'r', 'O']

2, 173, 637, 6477, 20, 3977, 2085, 14, 18, 12, 8397, 5857, 21, 21, 2, 18, 15