Exercise 2 solution

    import os, tempfile

    path = os.path.join(tempfile.gettempdir(), "all_bytes.bin")
    with open(path, "wb") as f:
        f.write(bytes(range(256)))

    with open(path, "rb") as f:
        data = f.read()

    print(len(data))                          # 256
    print(sum(1 for b in data if b >= 128))   # 128
    print(data[:4])                           # b'\x00\x01\x02\x03'

    with open(path, "rb") as f:
        f.seek(-5, os.SEEK_END)
        print(f.read().hex(" "))              # fb fc fd fe ff

    os.remove(path)

(Run as written; the output matched the comments.)

Explanation: bytes(range(256)) holds every possible byte value once, so
exactly half of them (128 to 255) are 128 or more. Opening with "rb" returns
bytes with no newline or encoding translation. seek(-5, os.SEEK_END) moves
to five bytes before the end of the file; a negative offset is only allowed
relative to the end (or the current position) in binary mode.