Python 3.8 Nested varible not updating

[Teknohead23]

If I use a while loop, which I think I should, I get an infinite loop as it will always be true

A for loop is always the first choice in Python,here a example with enumerate and f-string which you should use.

import os

letters = input("Enter the first 3 letters : ").upper()
num_start = 1
for index,item in enumerate(letters, num_start):
    dir_look = fr"C:\Users\user\Documents\Client Drawings\{letters}{index:03}"
    print(dir_look)
    check_for_folder = os.path.isdir(dir_look)
    print(check_for_folder

Output:
Enter the first 3 letters : aaa
C:\Users\user\Documents\Client Drawings\AAA001
False
C:\Users\user\Documents\Client Drawings\AAA002
False
C:\Users\user\Documents\Client Drawings\AAA003
False

I cant use enumerate as it's only going to iterate 3 times as there are 3 input letters, I tried using aaaa, and it iterates 4 times, but you get AAAA001
So for the programs purpose, it's not a viable solution