还要学生的存储信息文件

好的，根据你的需求，我们可以使用CSV文件来存储学生的信息。下面是修改后的代码示例：

import datetime
import csv

class ComputerRoom:
    def __init__(self):
        self.students = {}
        self.load_students()
    
    def add_student(self, id, name, cls, start_time):
        self.students[id] = {'name': name, 'class': cls, 'start_time': start_time}
        self.save_students()
    
    def end_session(self, id):
        start_time = self.students[id]['start_time']
        end_time = datetime.datetime.now()
        duration = end_time - start_time
        hours = duration.total_seconds() / 3600
        
        if hours < 0.5:
            cost = 1.0
        elif hours < 1:
            cost = 2.0
        elif hours < 3:
            cost = 2.0 * hours
        else:
            cost = 6.0 + (hours - 3) * 3.0
        
        print(f"{self.students[id]['name']}上机时长为{hours:.2f}小时，费用为{cost:.2f}元")
        del self.students[id]
        self.save_students()
    
    def query_student(self, id=None, name=None):
        if id:
            if id in self.students:
                print(f"{self.students[id]['name']}的上机时间为{self.students[id]['start_time']}")
            else:
                print(f"学号为{id}的学生未找到")
        elif name:
            found = False
            for id, student in self.students.items():
                if student['name'] == name:
                    print(f"{student['name']}的上机时间为{student['start_time']}")
                    found = True
            if not found:
                print(f"姓名为{name}的学生未找到")
    
    def check_duration(self, id):
        start_time = self.students[id]['start_time']
        end_time = datetime.datetime.now()
        duration = end_time - start_time
        hours = duration.total_seconds() / 3600
        
        if hours > 5:
            print(f"{self.students[id]['name']}已连续上机超过5小时，请注意休息！")
    
    def load_students(self):
        try:
            with open('students.csv', newline='') as csvfile:
                reader = csv.reader(csvfile)
                for row in reader:
                    id, name, cls, start_time = row
                    start_time = datetime.datetime.fromisoformat(start_time)
                    self.students[id] = {'name': name, 'class': cls, 'start_time': start_time}
        except FileNotFoundError:
            pass
    
    def save_students(self):
        with open('students.csv', 'w', newline='') as csvfile:
            writer = csv.writer(csvfile)
            for id, student in self.students.items():
                writer.writerow([id, student['name'], student['class'], student['start_time'].isoformat()])
    
    def run(self):
        while True:
            print("1. 输入学生信息")
            print("2. 结束上机")
            print("3. 查询学生信息")
            choice = input("请选择操作：")
            
            if choice == '1':
                id = input("请输入学生学号：")
                name = input("请输入学生姓名：")
                cls = input("请输入学生班级：")
                start_time = datetime.datetime.now()
                self.add_student(id, name, cls, start_time)
                print(f"{name}已成功登录计算机房，上机时间为{start_time}")
            elif choice == '2':
                id = input("请输入学生学号：")
                self.end_session(id)
            elif choice == '3':
                id = input("请输入学生学号（留空则按姓名查询）：")
                if id:
                    self.query_student(id=id)
                else:
                    name = input("请输入学生姓名：")
                    self.query_student(name=name)
            else:
                print("输入错误，请重新选择！")
                continue
            
            for id in self.students:
                self.check_duration(id)

在新的代码中，我们添加了`load_students`和`save_students`两个方法，用来读取和保存CSV文件。在程序启动时，会自动读取CSV文件中的学生信息，而在添加或结束上机时，会自动保存学生信息到CSV文件中。

注意，CSV文件中的时间是使用ISO格式存储的，可以使用`datetime.datetime.fromisoformat`方法将其转换为`datetime.datetime`类型。