Python学习（是我的课堂上学到的东西）不包含课外

2023-11-14课堂

下面是今天学的有关python的一些内容
归纳一下就是对封装装饰器，继承，多态的内容

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"""
    装饰器的封装
"""

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

    @property
    def age(self):
        print("get")
        return self.__age

    @age.setter
    def age(self,age):
        print("set")
        self.__age = age

s = Student("zhangsan", 18)
s.age = 21
print(s.age)
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"""
    类方法和静态方法的装饰器
"""

class Student:

    @classmethod
    def class_method(cls):
        print('class method')
        print(cls)

    @staticmethod
    def static_method():
        print('static method')

s = Student()
s.class_method()
Student.class_method()
Student.static_method()
s.static_method()
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"""
    类成员和实例成员
"""
class Student:
    id = 10
    name = "jack"
    def __init__(self,city,salary):
        self.city = city
        self.salary = salary

    @classmethod
    def class_method(cls):
        print("class_method")

    def instance_method(self):
        print("instance_method")

# 类成员
print(Student.id,Student.name)
Student.class_method()
# 实例成员
stu = Student("Hong Kong",10000)
print(stu.id,stu.name,stu.city,stu.salary)
stu.instance_method()
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"""
    继承：当一个类中定义的属性和方法需要在另一个类中直接使用，且该类和上一个类之间存在is a 的关系，就可以使用继承来实现属性和方法的重复使用
    - is a 的关系 Person Staff Staff is a Person（继承） Car is a cat（no）
    - 继承的实现
    class Student（person，staff）
"""

class Father:
    name = "jack"
    age = 40
    def teacher(self):
        print("teaching...")

class Son(Father):
    pass

s = Son()
print(s.name, s.age)
s.teacher()
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"""
    继承（多继承）
"""

class Person:
    name = "Person"
    age = 18
    def eat(self):
        print("Person eat")

class Staff:
    name = "Staff"
    age = 20
    def eat(self):
        print("Staff eat")

class Coder(Person, Staff):
    pass

c = Coder()
print(c.name, c.age)
c.eat()
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"""
    继承：会先创建父类对象再创建子类的对象
"""

class Animal:
    def __init__(self):
        print("Animal is created")

class Cat(Animal):
    # 注意：如果子类显示的定义了构造函数，需要手动调用父类的构造函数，如果子类没有定义构造函数，则会自动调用父类的构造函数
    def __init__(self):
        # 第一种方法：类
        # Animal.__init__(self)
        # 第二种方法：super()
        super().__init__()
        print("Cat is created")

cat = Cat()
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"""
    多态
"""

class Animal:
    def yell(self):
        pass

class Dog(Animal):
    def yell(self):
        print('汪汪汪')

class Cat(Animal):
    def yell(self):
        print('喵喵喵')

# 演示方式1
animal: Animal = Dog()
animal.yell()
animal: Animal = Cat()
animal.yell()
print("----------------")
# 演示方式2
animals: [Cat(), Dog()]
for animal in animals:
    animal.yell()
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-- 创建数据库
create database python;

-- 这里调用自己的数据库
use python;

-- 创建表
create table students(
    ID int primary key auto_increment,
    Name varchar(20) not null,
    Python float default 50.0,
    Java float default 60.0,
    C float default 0.0
);

-- 插入数据
insert into students(Name,Python,Java,C) values ("张三",90.5,60,55),
("李四",100,88,66),
("王五",77,58,43)
;

-- 查询数据
select * from students;
select Name,Python from students;
select ID,Name,Python from students where Python >=80;

-- 更新数据
update students set C = 60 where ID=1;

-- 删除数据
delete from students where id =3;

-- 删除全部数据
truncate table students;