Python/ciphers/baconian_cipher.py

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"""
Program to encode and decode Baconian or Bacon's Cipher
Wikipedia reference : https://en.wikipedia.org/wiki/Bacon%27s_cipher
"""
encode_dict = {
"a": "AAAAA",
"b": "AAAAB",
"c": "AAABA",
"d": "AAABB",
"e": "AABAA",
"f": "AABAB",
"g": "AABBA",
"h": "AABBB",
"i": "ABAAA",
"j": "BBBAA",
"k": "ABAAB",
"l": "ABABA",
"m": "ABABB",
"n": "ABBAA",
"o": "ABBAB",
"p": "ABBBA",
"q": "ABBBB",
"r": "BAAAA",
"s": "BAAAB",
"t": "BAABA",
"u": "BAABB",
"v": "BBBAB",
"w": "BABAA",
"x": "BABAB",
"y": "BABBA",
"z": "BABBB",
" ": " ",
}
decode_dict = {value: key for key, value in encode_dict.items()}
def encode(word: str) -> str:
"""
Encodes to Baconian cipher
>>> encode("hello")
'AABBBAABAAABABAABABAABBAB'
>>> encode("hello world")
'AABBBAABAAABABAABABAABBAB BABAAABBABBAAAAABABAAAABB'
>>> encode("hello world!")
Traceback (most recent call last):
...
Exception: encode() accepts only letters of the alphabet and spaces
"""
encoded = ""
for letter in word.lower():
if letter.isalpha() or letter == " ":
encoded += encode_dict[letter]
else:
raise Exception("encode() accepts only letters of the alphabet and spaces")
return encoded
def decode(coded: str) -> str:
"""
Decodes from Baconian cipher
>>> decode("AABBBAABAAABABAABABAABBAB BABAAABBABBAAAAABABAAAABB")
'hello world'
>>> decode("AABBBAABAAABABAABABAABBAB")
'hello'
>>> decode("AABBBAABAAABABAABABAABBAB BABAAABBABBAAAAABABAAAABB!")
Traceback (most recent call last):
...
Exception: decode() accepts only 'A', 'B' and spaces
"""
if set(coded) - {"A", "B", " "} != set():
raise Exception("decode() accepts only 'A', 'B' and spaces")
decoded = ""
for word in coded.split():
while len(word) != 0:
decoded += decode_dict[word[:5]]
word = word[5:]
decoded += " "
return decoded.strip()
if __name__ == "__main__":
from doctest import testmod
testmod()