To toggle first two bytes of any file, quickly

first-two-byte-toggler.py

#!/usr/bin/env python3
"""
Toggle the first & second bytes.
Syntax: python <py-file> filename
"""


import sys


def flip_first_bit(filename):
    with open(filename, "r+b") as fp:
        fp.seek(1, 0)
        byte_one = fp.read(1)
        byte_two = fp.read(1)
        fp.seek(-2, 1)
        fp.write(byte_two)
        fp.write(byte_one)


if __name__ == "__main__":
    filename = sys.argv[1]
    flip_first_bit(filename)