Excel Sheet Column Number

class Solution(object):
    def titleToNumber(self, columnTitle):
        """
        :type columnTitle: str
        :rtype: int
        """
        '''alpha_d = dict(zip([chr(x) for x in range(ord('A'), ord('Z')+1)], [y for y in range(1, 27)]))'''
        
        sn = 0
        
        if len(columnTitle)==1:
            sn += (ord(columnTitle)-ord('A')+1)
        else:
            for i, c in enumerate(columnTitle):
                # print(c, len(columnTitle[i:]))
                sn += (ord(c)-ord('A')+1) * pow(26,len(columnTitle[i+1:]))
        return sn
            
        
        '''def column_num(c, sn):
            if len(c)==1:
                sn += alpha_d[c]
                return sn
            else:
                sn += alpha_d[c[0]] * pow(26,len(c)-1)
                c = c[1:]
                sn = column_num(c, sn)
                return sn
                
        out = column_num(columnTitle, sum_num)
        return out
        
        
        res = 0
        for c in columnTitle:
            print(res)
            res = res*26 + ord(c)-ord('A')+1
            print(res)
        return res'''