python3 读取大文本最后指定行数内容

import sys
import os

import string#python2写法

RCV_LOG = r"C:\\Users\天宇\Desktop\\out"

def get_last_n_lines(logfile, n):
    n=int(n)#python3写法

#n = string.atoi(n)#python2写法
    blk_size_max = 4096
    n_lines = []
    with open(logfile, 'rb') as fp:
        fp.seek(0, os.SEEK_END)
        cur_pos = fp.tell()
        while cur_pos > 0 and len(n_lines) < n:
            blk_size = min(blk_size_max, cur_pos)
            fp.seek(cur_pos - blk_size, os.SEEK_SET)
            blk_data = fp.read(blk_size)
            assert len(blk_data) == blk_size
            lines = blk_data.split(b'\n')

            # adjust cur_pos
            if len(lines) > 1 and len(lines[0]) > 0:
                n_lines[0:0] = lines[1:]
                cur_pos -= (blk_size - len(lines[0]))
            else:
                n_lines[0:0] = lines
                cur_pos -= blk_size

            fp.seek(cur_pos, os.SEEK_SET)

    if len(n_lines) > 0 and len(n_lines[-1]) == 0:
        del n_lines[-1]
    return n_lines[-n:]

print(get_last_n_lines(RCV_LOG, "5"))