import mmap
import os


def file_last(file, count):
    with open("log.txt") as log:
        end = last_pos = os.stat("log.txt").st_size
        lines = []

        with mmap.mmap(log.fileno(), 0, access=mmap.ACCESS_READ) as mm:
            while last_pos != -1:

                last_pos = mm.rfind(b"\n", 0, last_pos)

                if last_pos != -1:
                    lines.append(mm[last_pos:end].strip().decode())
                    end = last_pos

                if len(lines) >= count:
                    break

    lines.reverse()
    return lines


last_lines = file_last("log.txt", 3)
for line in last_lines:
    print(line)