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加了文件，可使学生信息持久性保存在文件中。
注：即使退出循环或者程序，在下次进入系统的时候仍可读入学生信息数据。
一、代码
代码如下（示例）：
def print_menu():
print("""
==========================================
欢迎适用学生信息管理系统
1.添加学生信息
2.删除学生信息
3.修改学生信息
4.查询学生信息
5.统计学生成绩
6.显示所有学生信息
7.退出系统
==========================================
""")
def print_info(stu_info):
# print("学号", "姓名", "性别", "语文成绩", "数学成绩", "英语成绩",)
print("学号 姓 名 性 别 语文成绩 数学成绩 英语成绩")
for i in range(len(stu_info)):
print(stu_info[i], end=" " * 7)
#1.添加学生信息
def apendStudent():
print("你选择的选项是: 1.添加学生信息")
id = input("请输入你要添加的学生学号：")
for i in students:
if len(i) > 0 and i[0] == id:
print("该学生信息已保存")
break
else:
stu_info = input_info(id)
students.append(stu_info)
answer = input('是否继续添加？y/n\n')
if answer == 'y':
apendStudent()
else:
save_file()
print('学生信息录入完毕！！！')
# save_file()
# print("你添加的学生信息如下：")
# print_info(stu_info)
#2.删除学生信息
def delStudent():
print("你选择的选项是:2.删除学生信息")
id = input("请输入你要删除的学生学号：")
for i in students:
if len(i) > 0 and i[0] == id:
students.remove(i)
print("信息已刪除")
save_file()
break
else:
print("学生信息未保存")
#3.修改学生信息
def modifyStudent():
print("你选择的选项是:3.修改学生信息")
id = input("请输入你要修改的学生学号：")
for i in students:
if len(i) > 0 and i[0] == id:
stu_Id = students.index(i)
stu_info = input_info(id)
students[stu_Id] = stu_info
print("修改后的学生信息：")
print_info(stu_info)
save_file()
break
else:
print("学生信息未保存")
#4.查询学生信息
def searchStudent():
print("你选择的选项是:4.查询学生信息")
id = input("请输入你要查询的学生学号：")
for i in students:
if len(i) > 0 and i[0] == id:
print("查询的学生信息如下：")
print_info(i)
break
else:
print("学生信息未保存")
#输入学生信息
def input_info(id):
stu_id = id
name = input("姓名：")
sex = input("性别：")
ch_score = float(input("语文成绩："))
math_score = float(input("数学成绩："))
eng_score = float(input("英语成绩："))
stu_info = [stu_id, name, sex, ch_score, math_score, eng_score]
return stu_info
#5.统计学生成绩
def showStudent():
print("你选择的选项是:5.统计学生成绩")
id = input("请输入你要统计的学生学号：")
for i in students:
if len(i) > 0 and i[0] == id:
stu_score(i)
break
else:
print("学生信息未保存")
def stu_score(stu_info):
sum_score = stu_info[3] + stu_info[4] + stu_info[5]
avg_score = sum_score / 3
print("学生三门课程总成绩为：%.2f" % sum_score)
print("学生三门课程平均成绩为：%.2f" % avg_score)
#6.显示所有学生信息
def showAllStudent():
print("你选择的选项是:6.显示所有学生信息")
if len(students) > 0:
print("学号 姓名 性别 语文成绩 数学成绩 英语成绩 总成绩 平均成绩")
for i in range(len(students)):
sum_scores = students[i][3] + students[i][4] + students[i][5]
avg_scores = sum_scores / 3
print(students[i][0]," ",students[i][1]," ", students[i][2]," ",students[i][3]," ",students[i][4]," ",students[i][5]," ",sum_scores," ",avg_scores,"\n")
else:
print("暂无数据！")
#保存数据至文件中
def save_file():
f = open("student.txt", 'w', encoding='utf-8')
f.write(str(students))
f.close()
print("数据保存至student.txt文件成功！")
#将数据读取至变量中
def read_file():
try:
f = open('student.txt', 'r', encoding='utf-8')
ret = f.read()
global students
students = eval(ret)
f.close()
print("数据读取成功!")
except:
print("文件不存在")
stu_info = []
students = []
while True:
print_menu();
read_file();
select_no = input("请输入你的操作选项编号:")
if select_no == "1":
apendStudent();
elif select_no == "2":
delStudent();
elif select_no == "3":
modifyStudent();
elif select_no == "4":
searchStudent();
elif select_no == "5":
showStudent();
elif select_no == "6":
showAllStudent();
elif select_no == "7":
print("退出系统！")
break
else:
print("你输入的选项有误，请重新输入选项编号！")
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