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 sysimport getoptimport 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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