Tiny python 3.x script to solve atbash ciphers

pyatbash.py

s = input("Please enter the cipher text: ")

chars = "abcdefghijklmnopqrstuvwxyz"
exclude = " '\":;.,?!"

result = []

for c in s:
    if c in exclude:
        result.append(c)
    else:
        idx = 0 - (chars.index(c) + 1)
        result.append(chars[idx])

print("".join(result))