python打印文件的前几行或最后几行

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()
    

 

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