Convert spreadsheet number to column letter

Question

I\'m looking for the opposite to this Q&A: Convert an excel or spreadsheet column letter to its number in Pythonic fashion.

or this one but in python How to conv

Answer 1

My recipe for this was inspired by another answer on arbitrary base conversion (https://stackoverflow.com/a/24763277/3163607)

import string

def n2a(n,b=string.ascii_uppercase):
   d, m = divmod(n,len(b))
   return n2a(d-1,b)+b[m] if d else b[m]

Example:

for i in range(23,30):
    print (i,n2a(i))

outputs

23 X
24 Y
25 Z
26 AA
27 AB
28 AC
29 AD