Lempel-Ziv-Welch algorithm in Python

lzw.py

from math import floor, ceil
from typing import AnyStr


ASCII_TO_INT: dict = {i.to_bytes(1, 'big'): i for i in range(256)}
INT_TO_ASCII: dict = {i: b for b, i in ASCII_TO_INT.items()}


def compress(data: AnyStr) -> bytes:
    if isinstance(data, str):
        data = data.encode()
    keys: dict = ASCII_TO_INT.copy()
    n_keys: int = 256
    compressed: list = []
    start: int = 0
    n_data: int = len(data)+1
    while True:
        if n_keys >= 512:
            keys = ASCII_TO_INT.copy()
            n_keys = 256
        for i in range(1, n_data-start):
            w: bytes = data[start:start+i]
            if w not in keys:
                compressed.append(keys[w[:-1]])
                keys[w] = n_keys
                start += i-1
                n_keys += 1
                break
        else:
            compressed.append(keys[w])
            break
    bits: str = ''.join([bin(i)[2:].zfill(9) for i in compressed])
    return int(bits, 2).to_bytes(ceil(len(bits) / 8), 'big')


def decompress(data: AnyStr) -> bytes:
    if isinstance(data, str):
        data = data.encode()
    keys: dict = INT_TO_ASCII.copy()
    bits: str = bin(int.from_bytes(data, 'big'))[2:].zfill(len(data) * 8)
    n_extended_bytes: int = floor(len(bits) / 9)
    bits: str = bits[-n_extended_bytes * 9:]
    data_list: list = [int(bits[i*9:(i+1)*9], 2)
                       for i in range(n_extended_bytes)]
    previous: bytes = keys[data_list[0]]
    uncompressed: list = [previous]
    n_keys: int = 256
    for i in data_list[1:]:
        if n_keys >= 512:
            keys = INT_TO_ASCII.copy()
            n_keys = 256
        try:
            current: bytes = keys[i]
        except KeyError:
            current = previous + previous[:1]
        uncompressed.append(current)
        keys[n_keys] = previous + current[:1]
        previous = current
        n_keys += 1
    return b''.join(uncompressed)

Hi, I am new to python, just want to know how to use this code with any file, . means how to put data on this code. for example with open('text.txt, 'r') as f: data = f.read(). bur it says data over shadows. how i can put data into code so it can compress and decompress.
Thanks

@RashidAkh I didn’t use this code for years, it was just the reference solution I wrote for an exercice when I was teaching :)

If you download the file and put it in a given directory, write this in another Python file of the same directory:

import lzw

# Compresses "example file.txt" into "example file.txt.lzw".
with open('example file.txt') as input_file:
    with open('example file.txt.lzw', 'wb') as compressed_file:
        compressed_file.write(lzw.compress(input_file.read()))

# Decompresses and prints "example file.txt.lzw" content.
with open('example file.txt.lzw', 'rb') as compressed_file:
    print(lzw.decompress(compressed_file.read()))

Thank you so much, it worked very well for me. However, it appends b and puts the uncompressed text in ' '. I tried editing "return b''.join(uncompressed)" to "return uncompressed" but got an unexpected output.
Any solution?