head.py
# -*- coding: UTF-8 -*-#!/usr/bin/python# by Jakcing 2022.02.17# print first n lines or last n lines in big file import sysimport getoptimport linecacheVERSION="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_countdef 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 += 1try: 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()Python的优点有哪些
1、简单易用，与C/C++、Java、C# 等传统语言相比，Python对代码格式的要求没有那么严格；
2、Python属于开源的，所有人都可以看到源代码，并且可以被移植在许多平台上使用；
3、Python面向对象，能够支持面向过程编程,也支持面向对象编程；
4、Python是一种解释性语言，Python写的程序不需要编译成二进制代码，可以直接从源代码运行程序；
5、Python功能强大，拥有的模块众多，基本能够实现所有的常见功能。
