作业内容：
实现效果：
从info.txt文件中读取员工及其工资信息，最后将修改或增加的员工工资信息也写入原info.txt文件。
效果演示：
1. 查询员工工资
2. 修改员工工资
3. 增加新员工记录
4. 退出
思路：
进行文件读写，将读或写的数据利用strip和split方法，对文件内容进行增改查
代码：
#!/usr/bin/env python
# -*- coding:utf-8 -*-
# Author: Sean_Yao
"""工资管理系统作业"""
import sys
with open("info.txt", 'r', encoding="utf-8") as f:
file = list(f)
msg = '''
1. 查询员工工资
2. 修改员工工资
3. 增加新员工记录
4. 退出
'''
exit_flag = False
while not exit_flag:
print(msg)
index_user_choice = input('>>:')
if index_user_choice == '':
with open("info.txt", 'r', encoding="utf-8") as f:
user_salary = f.readlines()
username = input("请输入要查询的员工姓名（例如：Alex）：")
for user_line in user_salary:
(user,salary) = user_line.strip('\n').split()
if username == user:
print('%s 的工资是：%s ' % (username,salary))
pass elif index_user_choice == '':
old_user = input("输入员工姓名（例如：Alex）：").strip()
for i in file:
file = i.strip().split()
if old_user in file:
old_salary = file[1]
new_user,new_salary = input("请输入更改后员工姓名和工资，用空格分隔（例如：Alex 10）：").strip().split()
with open("info.txt", "r", encoding="utf-8") as f:
lines = f.readlines()
with open("info.txt", "w", encoding="utf-8") as f_a:
for line in lines:
if old_user in line:
line = line.replace(old_user,new_user)
f_a.write(line)
f_a.close()
with open("info.txt", "r", encoding="utf-8") as f:
lines = f.readlines()
with open("info.txt", "w", encoding="utf-8") as f_b:
for line in lines:
if new_user in line:
line = line.replace(old_salary,new_salary)
f_b.write(line)
f_b.close()
print("修改成功") elif index_user_choice == '':
f = open('info.txt', 'r+', encoding='utf-8')
user_salary = f.readlines()
new_user_new_salary = input("请输入要增加的员工姓名和工资，共空格分割（例如：Eric 100000）：")
f.write(new_user_new_salary + '\n')
f.close()
elif index_user_choice == '':
sys.exit("再见")
else:
print('输入操作无效！')
info.txt文件内容：
Alex 100000 Rain 80000 Egon 50000 Yuan 30000