1.声明⼀个电脑类: 属性:品牌、颜⾊、内存⼤小 方法:打游戏、写代码、看视频

a.创建电脑类的对象，然后通过对象点的⽅方式获取、修改、添加和删除它的属性
b.通过attr相关⽅方法去获取、修改、添加和删除它的属性

import random
class Computer:
    """电脑类"""
    def __init__(self, brand, color, ram):
        self.brand = brand
        self.color = color
        self.ram = ram

    def paly_game(self):     # 有波浪号警告，说明选的方法不对
        return '打游戏'

    def write_code(self, lang: str):
        return '写%s代码' % lang

    def watch_video(self):
        return '看视频'

c1 = Computer('华为', '白色', '512G')
print(c1.brand)   # 华为
c1.color = '黑色'
print(c1.color) # 黑色
c1.price = '1000'
print(c1.price)  # 1000
# del c1.price
# print(c1.price)  # AttributeError: 'Computer' object has no attribute 'price'

print(getattr(c1, 'brand'))    # 华为
setattr(c1, 'color', '红色')
print(c1.color)      # 红色
setattr(c1, 'price', 200)
print(c1.price)   # 200
# delattr(c1, 'price')
# print(c1.price)  # AttributeError: 'Computer' object has no attribute 'price'

2.声明⼀个人的类和狗的类:

狗的属性:名字、颜⾊、年龄
狗的⽅方法:叫唤
人的属性:名字、年龄、狗
人的⽅方法:遛狗
a.创建⼈的对象小明，让他拥有一条狗大黄，然后让小明去遛大黄

class Dog:
    """狗"""
    def __init__(self, name, color, age):
        self.name = name
        self.color = color
        self.age = age

    def shout(self):
       print('%s在叫：汪汪汪' % self.name)


class Person:
    """人类"""
    def __init__(self, name, age):
        self.name = name
        self.age = age      # 拥有年龄
        self.dog = None   # 狗类的对象，具体的某只狗

    def walk_the_dog(self):
        if not self.dog:
            print('没有狗')
        else:
            print('%s牵着%s在散步' % (self.name, self.dog.name))

p1 = Person('小明', 35)   # 创建人的对象   ？？没有声明self.dog就能用？
dog1 = Dog('大黄', '白色', 5)  # 创建狗的对象
p1.dog = dog1 # 让人拥有狗
p1.walk_the_dog()

3.声明⼀圆类，自己确定有哪些属性和方法

class Circle:
    pi = 3.1415926

    def __init__(self, radius):
        self.radius = radius

    def perimeter(self):
        return 2 * Circle.pi * self.radius

    def area(self):
        return Circle.pi * self.radius ** 2
c1 = Circle(3)
print(c1.perimeter())
print(c1.area())

4.创建一个学⽣生类:

属性:姓名，年龄，学号
方法:答到，展示学⽣生信息
创建⼀个班级类:
属性:学生，班级名
方法:添加学⽣，删除学生，点名, 求班上学生的平均年龄

class Student:
    def __init__(self, name, age=0, study_id='000'):
        self.name = name
        self.age = age
        self.study_id = study_id
        self.is_in_class = random.randint(0,1)


    def respond(self):
        print('%s,到!' % self.name)

    def show(self):
        print('姓名：%s 年龄：%d 学号：%s') % (self.name, self.age, self.study_id)


class Class:
    def __init__(self, class_name):
        self.students = [] # 一个班有多个学生：一个列表，列表中的元素是学生
        self.class_name = class_name
        def func():
            num = 1
            while True:
                yield 'stu'+str(num)
                num += 1
        self.creat_id = func()  # 学号生成器


    def add_student(self):
        name = input('学生姓名；')
        age = int(input('学生的年龄：'))
        study_id = next(self.creat_id)
        stu = Student(name, age, study_id)
        self.students.append(stu)

    def del_student(self):
        """删除学生"""
        del_name = input('请输入要删除的学生的名字：')
        flag = False
        for stu in self.students:
            if stu.name == del_name:
                flag = True
                stu.show()
                input('是否删除（y/n）')
                if value == 'y':
                    self.students.remove(stu)
        if not flag:
            print('没有该学生！')

    def call_name(self):
        """点名"""
        for stu in self.students:
            print(stu.name)
            if stu.is_in_class:
                stu.respond()

    def avg_age(self):
        """求平均年龄"""
        ages = 0
        for stu in self.students():
            ages += stu.age
        return ages / len(self.students)



    def show_all_students(self):
        print('=========%s的学生============')
        for stu in self.students:
            stu.show()

c1 = Class('py1903')
c2 = Class('py1904')
c1.add_student()    # 001
c1.add_student()    # 002
c2.add_student()    # 001
c1.add_student()    # 003
c1.show_all_students()
c2.show_all_students()