python打印文件的前几行或最后几行教程

写一个类似linux head的小工具，在window下用。

head.py 

# -*- coding: UTF-8 -*-
#!/usr/bin/python
# by Jakcing 2019.02.17
# print first n lines or last n lines in big file

import sys
import getopt
import linecache

VERSION="1.1"

def get_line_count(filename):
line_count = 0
file = open(filename,'r+', encoding='utf-8')
while True:
buffer = file.read(8192 * 1024 )
if not buffer:
 break
line_count += buffer.count('\n')
file.close()
return line_count

def read_head_line(flist, line_num):
for file_name in flist:
print("===％s===" ％ file_name)
f = open(file_name, 'r', encoding='utf-8')
if(f):
 for i in range(line_num):
 print(f.readline(), end='')

def read_last_line(flist, line_num):

for file_name in flist:

linecache.clearcache()
line_count = get_line_count(file_name)
print('===％s=== line count total: ％d' ％ (file_name, line_count))
line_count = line_count - line_num +1
print('===％s=== line ％d to end' ％ (file_name, line_count))

for i in range(line_num):
 last_line = linecache.getline(file_name, line_count) #从第line_count行读起
 print('line[％d]:％s' ％ (line_count, last_line), end='')
 line_count += 1

try:
opts, args = getopt.getopt(sys.argv[1:], "hvn:t:", ["help", "output=", "numline=", "tail=", "version"])
except getopt.GetoptError:
 print("argv error,please input")

for cmd, arg in opts:
if cmd in ("-h", "--help"):
print("usage: head.py -n number filename \nor head.py -t number filename")
sys.exit()
elif cmd in ("-n", "--numline"): #打印文件开头的line_num行
line_num=int(arg)
file_names=args[:]
read_head_line(file_names, line_num)
elif cmd in ("-t", "--tail"): #打印文件结尾的line_num行
line_num=int(arg)
file_names=args[:]
read_last_line(file_names, line_num)

elif cmd in ("-v", "--version"):
print("％s ％s" ％ (sys.argv[0], VERSION))

sys.exit()

来源：https://blog.csdn.net/william_djj/article/details/87537318