Excel Sheet Column Number

Problem Statement:

Given a column title as appear in an Excel sheet, return its corresponding column number.
For example:

    A -> 1
    B -> 2
    C -> 3
    ...
    Z -> 26
    AA -> 27
    AB -> 28 
    ...

Example 1:
Input: "A"
Output: 1

Example 2:
Input: "AB"
Output: 28

Example 3:
Input: "ZY"
Output: 701


Solution:
class Solution:
    def titleToNumber(self, s: str) -> int:
        ######## O(N): O(1)
        column={
            "A":1,"B":2,"C":3,"D":4,"E":5,"F":6,"G":7,"H":8,"I":9,"J":10,"K":11,"L":12,"M":13,"N":14,"O":15,"P":16,
            "Q":17,"R":18,"S":19,"T":20,"U":21,"V":22,"W":23,"X":24,"Y":25,"Z":26}
        
        def recurse(s,power):
            if len(s)==1:
                return column[s]
            sm=(26**power)*column[s[0]]+recurse(s[1:],power-1)
            return sm
        return recurse(s,len(s)-1)