Dictionary Encoding

Example Application: Text

Composed of a dictionary and message. Common sequences of characters (may be handled as, i.e., words) are replaced with dictionary references.

Implementation

class EncodedMessage:
    def __init__(self, message: str, dictionary: list[str]):
        self.message = message
        self.dictionary = dictionary
 
    def __str__(self):
        return self.message
 
 
def perform_encoding(string: str) -> EncodedMessage:
    words = string.split(" ")
 
    # Tally the frequency of each word
    dict_words = {}
    for word in words:
        if word in dict_words and not word.isnumeric():
            dict_words[word] += 1
        else:
            dict_words[word] = 1
 
    # Form a dictionary of repeating words
    repeating_words = [word for word in dict_words if dict_words[word] > 1]
 
    repeating_words_dict = {  # Used to quickly find the index of a word rather than searching through the list
        word: index for index, word in enumerate(repeating_words)
    }
 
    # Encode the words
    encoded_string = ""
    for word in words:
        if word in repeating_words:
            encoded_string += f"{repeating_words_dict[word]} "
        else:
            encoded_string += f"{word} "
 
    return EncodedMessage(encoded_string[:-1], repeating_words)
 
 
def perform_decoding(encoded_message: EncodedMessage) -> str:
    words = encoded_message.message.split(" ")
    decoded_message = ""
    for word in words:
        if word.isnumeric():
            decoded_message += f"{encoded_message.dictionary[int(word)]} "
        else:
            decoded_message += f"{word} "
    return decoded_message[:-1]
 
 
message = (
    "ask not what your country can do for you but what you can do for your country"
)
encoded_message = perform_encoding(message)
decoded_message = perform_decoding(encoded_message)
print(f"Encoded message: {encoded_message}")
print(f"Decoded message: {decoded_message}")
print(f"Passed test? {message == decoded_message}")

Example

ask not what your country can do for you but what you can do for your country