一.利用b模式，编写一个cp工具，要求如下：
1. 既可以拷贝文本又可以拷贝视频，图片等文件
2. 用户一旦参数错误，打印命令的正确使用方法，如usage: cp source_file target_file
提示：可以用import sys，然后用sys.argv获取脚本后面跟的参数
#!/usr/bin/env python3# -*- coding:utf-8 -*-# cp工具import sysif len(sys.argv) != 3: print("usage: cp source_file target_file") sys.exit()else: source_file, target_file = sys.argv[1], sys.argv[2] with open(source_file,"rb") as read_f,open(target_file,"wb") as write_f: for line in read_f: write_f.write(line) 二.Python实现 tail -f 功能
#!/usr/bin/env python3# -*- coding:utf-8 -*-#tail -f工具import sys,timeif len(sys.argv) != 2: print("usage: tail file_name") sys.exit()else: file_name = sys.argv[1] with open(file_name,'rb') as f: f.seek(0,2) # 每次都从文件末尾开始读 while True: line = f.readline() if line: print(line.decode('utf-8'),end='') # 读取的每一行都去掉行尾的换行符 time.sleep(1) 有待优化，每次打开应该显示最后10行。
三.文件的修改
文件的数据是存放于硬盘上的，因而只存在覆盖、不存在修改这么一说，我们平时看到的修改文件，都是模拟出来的效果，具体的说有两种实现方式：
方式一：将硬盘存放的该文件的内容全部加载到内存，在内存中是可以修改的，修改完毕后，再由内存覆盖到硬盘（word，vim，nodpad++等编辑器）
import oswith open('a.txt') as read_f,open('.a.txt.swap','w') as write_f: data=read_f.read() #全部读入内存,如果文件很大,会很卡 data=data.replace('alex','SB') #在内存中完成修改 write_f.write(data) #一次性写入新文件os.remove('a.txt')os.rename('.a.txt.swap','a.txt') 方式二：将硬盘存放的该文件的内容一行一行地读入内存，修改完毕就写入新文件，最后用新文件覆盖源文件
import oswith open('a.txt') as read_f,open('.a.txt.swap','w') as write_f: for line in read_f: line=line.replace('alex','SB') write_f.write(line)os.remove('a.txt')os.rename('.a.txt.swap','a.txt') 三.全局替换程序：
-
写一个脚本，允许用户按以下方式执行时，即可以对指定文件内容进行全局替换
- 替换完毕后打印替换了多少处内容
#!/usr/bin/env python3# -*- coding:utf-8 -*-import sysimport osif len(sys.argv) != 4: print("usage: python3 replace old_str new_str filename") sys.exit()else: old_str = sys.argv[1] new_str = sys.argv[2] filename = sys.argv[3] filename_swap = sys.argv[3] + ".swap" with open(filename,"r",encoding="utf-8") as read_f,open(filename_swap,"w",encoding="utf-8") as write_f: count = 0 for line in read_f: line = line.replace(old_str,new_str) write_f.write(line) num = line.count(new_str) count += 1 totle = count * num print("一共替换了%s处内容" % totle) os.remove(filename) os.rename(filename_swap,filename) 四.模拟登陆：
- 用户输入帐号密码进行登陆
- 用户信息保存在文件内
- 用户密码输入错误三次后锁定用户，下次再登录，检测到是这个用户也登录不了
user_list.txt
wss:123:1alex:456:1jay:789:1
#!/usr/bin/env python3# -*- encoding: utf8 -*-import getpassimport osuser_dict = {}with open("user_list.txt", "r", encoding="utf-8") as user_list_flie: for line in user_list_flie.readlines(): user_list = line.strip().split(":") # print(user_list) _user = user_list[0].strip() _pwd = user_list[1].strip() _lockaccount = int(user_list[2].strip()) user_dict[_user] = {"user": _user, "pwd": _pwd, "lockaccount": _lockaccount} # print(user_dict[_username]) # print(user_dict)exit_flag = Falsecount = 0while count < 3 and not exit_flag: user = input('\n请输入用户名:') if user not in user_dict: count += 1 print("\n用户名错误") elif user_dict[user]["lockaccount"] > 0: print("\n用户已被锁定,请联系管理员解锁后重新尝试") break else: while count < 3 and not exit_flag: pwd = getpass.getpass('\n请输入密码:') # pwd = input('\n请输入密码:') if pwd == user_dict[user]["pwd"]: print('\n欢迎登陆') print('..........') exit_flag = True else: count += 1 print('\n密码错误') continue if count >= 3: # 尝试次数大于等于3时锁定用户 if user == "": print("\n您输入的错误次数过多,且用户为空") elif user not in user_dict: print("\n您输入的错误次数过多,且用户 %s 不存在" % user) else: user_dict[user]["lockaccount"] += 1 # print(user_dict[user]["lockaccount"]) with open("user_list.txt", "r", encoding="utf-8") as user_list_file, open("use_list.txt.swap", "w",encoding="utf-8") as new_user_list_file: for new_line in user_dict: new_user_list = [str(user_dict[new_line]["user"]), str(user_dict[new_line]["pwd"]), str(user_dict[new_line]["lockaccount"])] # print(new_user_list) user_str = ":".join(new_user_list) print(user_str) new_user_list_file.write(user_str + "\n") os.remove("user_list.txt") os.rename("use_list.txt.swap", "user_list.txt") print("\n您输入的错误次数过多,%s 已经被锁定" % user)