AI0814_jiaoan_public/w0_d6/06_students_persistence_json.py

"""
06 数据持久化版本：学生增删改查

持久化：
    程序运行时，数据在内存里。
    程序结束后，内存数据会消失。
    如果希望下次打开程序还能看到数据，就要把数据保存到文件或数据库。

本文件使用 JSON 文件保存数据。
运行后会在当前目录生成 students.json。
"""

import json
from pathlib import Path


DATA_FILE = Path("students.json")


class Student:
    def __init__(self, student_id, name, age, phone):
        self.id = student_id
        self.name = name
        self.age = age
        self.phone = phone

    def to_dict(self):
        return {
            "id": self.id,
            "name": self.name,
            "age": self.age,
            "phone": self.phone,
        }

    @classmethod
    def from_dict(cls, data):
        return cls(
            data["id"],
            data["name"],
            data["age"],
            data["phone"],
        )

    def __str__(self):
        return f"ID: {self.id}, 姓名: {self.name}, 年龄: {self.age}, 电话: {self.phone}"


class StudentManager:
    def __init__(self):
        self.students = []
        self.next_id = 1
        self.load()

    def load(self):
        if not DATA_FILE.exists():
            return

        with DATA_FILE.open("r", encoding="utf-8") as file:
            data = json.load(file)

        self.next_id = data.get("next_id", 1)
        self.students = [
            Student.from_dict(item)
            for item in data.get("students", [])
        ]

    def save(self):
        data = {
            "next_id": self.next_id,
            "students": [student.to_dict() for student in self.students],
        }
        with DATA_FILE.open("w", encoding="utf-8") as file:
            json.dump(data, file, ensure_ascii=False, indent=2)

    def add_student(self):
        name = input("姓名：").strip()
        age = input("年龄：").strip()
        phone = input("电话：").strip()
        self.students.append(Student(self.next_id, name, age, phone))
        self.next_id += 1
        self.save()
        print("添加成功")

    def list_students(self):
        if not self.students:
            print("暂无学生")
            return
        for student in self.students:
            print(student)

    def find_student_by_id(self, student_id):
        for student in self.students:
            if str(student.id) == str(student_id):
                return student
        return None

    def search_student(self):
        keyword = input("请输入要查询的姓名：").strip()
        result = [student for student in self.students if student.name == keyword]

        if not result:
            print("没有找到该学生")
            return

        for student in result:
            print(student)

    def update_student(self):
        student_id = input("请输入要修改的学生 ID：").strip()
        student = self.find_student_by_id(student_id)

        if student is None:
            print("没有找到该学生")
            return

        student.name = input("新姓名：").strip()
        student.age = input("新年龄：").strip()
        student.phone = input("新电话：").strip()
        self.save()
        print("修改成功")

    def delete_student(self):
        student_id = input("请输入要删除的学生 ID：").strip()
        student = self.find_student_by_id(student_id)

        if student is None:
            print("没有找到该学生")
            return

        self.students.remove(student)
        self.save()
        print("删除成功")


class Application:
    def __init__(self):
        self.manager = StudentManager()
        self.menu = {
            "1": ("添加学生", "add_student"),
            "2": ("查看所有学生", "list_students"),
            "3": ("查询学生", "search_student"),
            "4": ("修改学生", "update_student"),
            "5": ("删除学生", "delete_student"),
        }

    def show_menu(self):
        print("\n====== 学生管理系统：JSON 持久化版本 ======")
        for key, value in self.menu.items():
            title, _ = value
            print(f"{key}. {title}")
        print("0. 退出")

    def run(self):
        while True:
            self.show_menu()
            choice = input("请输入操作编号：").strip()

            if choice == "0":
                print("程序结束")
                break

            if choice not in self.menu:
                print("输入有误，请重新输入")
                continue

            _, method_name = self.menu[choice]
            getattr(self.manager, method_name)()


if __name__ == "__main__":
    app = Application()
    app.run()