Python_Note2

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def calculator():
    """
    命令行计算器，支持加、减、乘、除运算
    """
    print("欢迎使用命令行计算器")
    print("支持的操作：+ (加), - (减), * (乘), / (除)")
    print("输入 'exit' 退出程序")

    while True:
        try:
            # 获取用户输入
            user_input = input("请输入表达式 (例如 2 + 3): ").strip()

            # 退出条件
            if user_input.lower() == 'exit':
                print("感谢使用计算器，再见！")
                break

            # 解析输入
            parts = user_input.split()
            if len(parts) != 3:
                print("错误：请输入有效的表达式，如 '2 + 3'")
                continue

            num1, operator, num2 = parts

            # 转换数字
            num1 = float(num1)
            num2 = float(num2)

            # 执行计算
            if operator == '+':
                result = num1 + num2
            elif operator == '-':
                result = num1 - num2
            elif operator == '*':
                result = num1 * num2
            elif operator == '/':
                if num2 == 0:
                    print("错误：除数不能为零")
                    continue
                result = num1 / num2
            else:
                print(f"错误：不支持的运算符 '{operator}'")
                continue

            # 显示结果
            print(f"结果: {result}")

        except ValueError:
            print("错误：请输入有效的数字")
        except Exception as e:
            print(f"发生错误: {e}")


if __name__ == "__main__":
    calculator()

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import json


STUDENT_FILE = "students.json"

def load_students():
    """从文件加载学生数据"""
    try:
        with open(STUDENT_FILE, 'r') as f:
            return json.load(f)
    except FileNotFoundError:
        return {}
    except json.JSONDecodeError:
        print("警告: 数据文件损坏，将使用空数据库")
        return {}

def save_students(students):
    """保存学生数据到文件"""
    with open(STUDENT_FILE, 'w') as f:
        json.dump(students, f, indent=2)

def add_student(students):
    """添加新学生"""
    student_id = input("请输入学号: ").strip()
    if not student_id:
        print("学号不能为空！")
        return

    if student_id in students:
        print("该学号已存在！")
        return

    name = input("请输入姓名: ").strip()
    if not name:
        print("姓名不能为空！")
        return

    try:
        chinese = float(input("请输入语文成绩: "))
        math = float(input("请输入数学成绩: "))
        english = float(input("请输入英语成绩: "))
    except ValueError:
        print("成绩必须为数字！")
        return

    students[student_id] = {
        'name': name,
        'scores': {
            '语文': chinese,
            '数学': math,
            '英语': english
        },
        'total': chinese + math + english,
        'average': (chinese + math + english) / 3
    }
    save_students(students)
    print("学生信息已添加！")

def query_student(students):
    """查询学生信息"""
    student_id = input("请输入要查询的学号: ").strip()
    student = students.get(student_id)

    if student:
        print("\n学生信息:")
        print(f"学号: {student_id}")
        print(f"姓名: {student['name']}")
        print("成绩:")
        for subject, score in student['scores'].items():
            print(f"  {subject}: {score}")
        print(f"总分: {student['total']}")
        print(f"平均分: {student['average']:.2f}")
    else:
        print("未找到该学生！")

def list_students(students):
    """列出所有学生"""
    if not students:
        print("当前没有学生记录！")
        return

    print("\n学生列表:")
    print("学号\t姓名\t语文\t数学\t英语\t总分\t平均分")
    for student_id, info in students.items():
        scores = info['scores']
        print(f"{student_id}\t{info['name']}\t{scores['语文']}\t{scores['数学']}\t{scores['英语']}\t{info['total']}\t{info['average']:.2f}")

def update_student(students):
    """更新学生信息"""
    student_id = input("请输入要更新的学号: ").strip()
    if student_id not in students:
        print("未找到该学生！")
        return

    print("\n当前学生信息:")
    print(f"姓名: {students[student_id]['name']}")
    print("成绩:")
    for subject, score in students[student_id]['scores'].items():
        print(f"  {subject}: {score}")

    try:
        chinese = float(input("请输入新的语文成绩: "))
        math = float(input("请输入新的数学成绩: "))
        english = float(input("请输入新的英语成绩: "))
    except ValueError:
        print("成绩必须为数字！")
        return

    students[student_id]['scores'] = {
        '语文': chinese,
        '数学': math,
        '英语': english
    }
    students[student_id]['total'] = chinese + math + english
    students[student_id]['average'] = (chinese + math + english) / 3
    save_students(students)
    print("学生信息已更新！")

def delete_student(students):
    """删除学生"""
    student_id = input("请输入要删除的学号: ").strip()
    if student_id in students:
        del students[student_id]
        save_students(students)
        print("学生信息已删除！")
    else:
        print("未找到该学生！")

def student_management():
    """学生成绩管理系统主函数"""
    students = load_students()

    while True:
        print("\n学生成绩管理系统")
        print("1. 添加学生")
        print("2. 查询学生")
        print("3. 列出所有学生")
        print("4. 更新学生信息")
        print("5. 删除学生")
        print("6. 退出")

        choice = input("请选择操作 (1-6): ").strip()

        if choice == '1':
            add_student(students)
        elif choice == '2':
            query_student(students)
        elif choice == '3':
            list_students(students)
        elif choice == '4':
            update_student(students)
        elif choice == '5':
            delete_student(students)
        elif choice == '6':
            print("再见！")
            break
        else:
            print("无效的选择，请输入1-6之间的数字！")


if __name__ == "__main__":
    student_management()