Tiny python 3.x script to solve simple ceaser ciphers

pyceaser.py

import re

s = input("Please enter the cipher text: ")
place = input(
    "Please enter the character index (optional): ")
shift = input("Please enter the shift key: ")

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

result = []
exclude_count = 0

for i, c in enumerate(s, start=1):
    if c in exclude:
        exclude_count += 1
        result.append(c)
    elif place != "" and (i - exclude_count) % int(place) != 0:
        result.append(c)
    else:
        idx = chars.index(c)
        result.append(chars[idx - int(shift)])


print("".join(result))