Easy decryptor for Caesar cipher written in Python (maybe not the best variant, but the clearest one for me)

Caesar cipher decryptor

# coding=utf-8

__author__ = 'Iurii Sergiichuk'

# Text to decrypt
text = u"ТЙШЛЙРН ВЧУ ЭНЩХ ЫЙМЕХД? ЧУЗИЕ ИЙХЛН УЧЖЙЧ: ИЛШФЖ"
# Alphabet that encrypted message consists of (means, that in encrypted message only this letters can be encrypted)
ALPHABET = u'АБВГДЕЁЖЗИЙКЛМНОПРСТУФХЦЧШЩЪЫЬЭЮЯ'
alphabet_len = len(ALPHABET)
letter_map = {}
ord_map = {}
i = 0
for letter in ALPHABET:
    letter_map[letter] = i
    ord_map[i] = letter
    i += 1
variants = []
for i in range(alphabet_len):
    variant = []
    for char in text:
        possible_char = char
        possible_ord = letter_map.get(char)
        if possible_ord is not None:
            possible_ord += i
            possible_ord %= alphabet_len
            possible_char = ord_map.get(possible_ord)
        variant.append(possible_char)
    variants.append(variant)

for var in variants:
    str = ''
    for char in var:
        str += char
    print str