xor.py

import sys


def xor_each_byte(input_fname: str, xor_key: int, output_fname: str):
    with open(input_fname, 'rb') as f:
        bytes_arr = bytes([b^xor_key for b in f.read()])
    with open(output_fname, 'wb') as f:
        f.write(bytes_arr)


if __name__ == "__main__":
    input_fname, xor_key, output_fname \
        = sys.argv[1], int(sys.argv[2]), sys.argv[3]
    xor_each_byte(input_fname, xor_key, output_fname)