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 sys
if 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,time
if 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。
https://www.cnblogs.com/shengxinjing/p/5397145.html
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 os
with 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 os
with 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 sys
import os
if 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:123:1 alex:456:1 jay:789:1
#!/usr/bin/env python3
# -*- encoding: utf8 -*-
import getpass
import os
user_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 = False
count = 0
while count < 3 and not exit_flag:
user = input('
请输入用户名:')
if user not in user_dict:
count += 1
print("
用户名错误")
elif user_dict[user]["lockaccount"] > 0:
print("
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('
请输入密码:')
# pwd = input('
请输入密码:')
if pwd == user_dict[user]["pwd"]:
print('
欢迎登陆')
print('..........')
exit_flag = True
else:
count += 1
print('
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("
您输入的错误次数过多,且用户为空")
elif user not in user_dict:
print("
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 + "
")
os.remove("user_list.txt")
os.rename("use_list.txt.swap", "user_list.txt")
print("
您输入的错误次数过多,%s 已经被锁定" % user)