reverse.py

import os
import sys

arg = sys.argv[1]

start = os.getcwd()

os.mkdir('tmp')
os.chdir('tmp')

for c in arg:
    os.mkdir(c)
    os.chdir(c)

output = ''
while os.getcwd() != start:
    os.chdir('..')
    d = os.listdir()
    if len(d) > 1:
        os.rmdir('tmp')
        break
    [d] = d
    os.rmdir(d)
    output += d

print(output)