python基础语法17 面向对象3 多态,抽象类,鸭子类型,classmethod与staticmethod,isinstance与issubclass,反射

# 动物类
class Animal:
    # 方法 吃
    def eat(self):
        pass
    # 方法 叫
    def speak(self):
        pass
# 猪类
class Pig(Animal):
    def eat(self):
        print(‘bia唧...‘)

    def speak(self):
        print(‘哼哼哼...‘)
# 猫类
class Cat(Animal):
    def eat(self):
        print(‘咬ji 咬ji....‘)
    def speak(self):
        print(‘喵喵喵...‘)
# 狗类
class Dog(Animal):
    def eat(self):
        print(‘舔 ji 舔ji...‘)
    def speak(self):
        print(‘汪汪汪...‘)

animal1 = Dog()
animal2 = Pig()
animal3 = Cat()

# 让动物们叫起来
animal1.speak()
animal2.speak()
animal3.speak()

import abc

# 父类
class Animal(metaclass=abc.ABCMeta):
    # 方法 吃
    @abc.abstractmethod
    def eat(self):
        pass
    # 方法 叫
    @abc.abstractmethod
    def speak(self):
        pass

# 猪类
class Pig(Animal):
    def run(self):
        pass
    def eat(self):
        print(‘bia唧...‘)
    def speak(self):
        print(‘哼哼哼...‘)

print(Pig.__dict__)
print(Animal.__dict__)
pig_obj = Pig()

# 猪类
class Pig:
    def eat(self):
        print(‘bia唧...‘)
    def speak(self):
        print(‘哼哼哼...‘)
# 猫类
class Cat:
    def eat(self):
        print(‘咬ji 咬ji...‘)
    def speak(self):
        print(‘喵喵喵...‘)
# 狗类
class Dog:
    def eat(self):
        print(‘舔 ji 舔ji...‘)
    def speak(self):
        print("汪汪汪...")

# 猪类
class Pig:
    def eat(self):
        print(‘bia唧...‘)
    def speak(self):
        print(‘哼哼哼...‘)
# 猫类
class Cat:
    def eat(self):
        print(‘咬ji 咬ji...‘)
    def speak(self):
        print(‘喵喵喵...‘)
# 狗类
class Dog:
    def eat(self):
        print(‘舔 ji 舔ji...‘)
    def speak(self):
        print("汪汪汪...")

dog = Dog()
pig=Pig()
cat=Cat()

# 多态之炫技
def SPEAK(animal):
    animal.speak()

SPEAK(dog)
SPEAK(cat)
SPEAK(pig)

str1 = ‘tank is very handsome!!!‘
list1 = [‘tank‘, ‘is‘, ‘very‘, ‘handsome!!!‘]

# 自定义统计长度函数
def LEN(obj):
    return obj.__len__()

print(LEN(str1))    # 24
print(LEN(list1))   # 4

# classmethod_Demo:
class DB:
    __data = ‘tank is very handsome!!!‘
    def __init__(self, user, pwd, role):
        self.user = user
        self.pwd = pwd
        self.role = role

    # @classmethod
    # def init(cls, user, pwd, role):  # cls --》指的是类
    #     # 在类方法内部调用类产生一个实例 ---》 对象
    #     return cls(user, pwd, role)

    # 查看数据方法
    @classmethod
    def check_db(cls, user, pwd, role):  # cls --》指的是类
        # 在类方法内部调用类产生一个实例 ---》 对象
        obj = cls(user, pwd, role)
        # 1.查看数据前，必须要通过校验
        if obj.user == ‘tank‘ and obj.pwd == ‘123‘ and obj.role == ‘admin‘:
            print(‘检验通过..‘)
            print(cls.__data)
            return cls.__data

DB.check_db(‘tank‘, ‘123‘, ‘admin‘)

obj=DB(‘tank‘,‘123‘,‘admin‘)
obj.check_db(‘tank‘,‘123‘,‘admin‘)  # 也可以,第一个传入参数依然是类,但没什么意义

# staticmethod_Demo:
class Foo:
    @staticmethod
    def func(res):
        print(res)
obj = Foo()
#对象调用非绑定方法
obj.func(123)
#类调用非绑定方法
Foo.func(1234)

import uuid  # 用于产生随机字符串的模块

# 由时间戳以及某种算法组合而成，会产生一串世界上独一无二字符串。
print(uuid.uuid4()) # f93f9c3b-eef4-4001-922e-2124b48ca7ab

# isinstance:
class Foo:
    pass

class Boo:
    pass

foo_obj = Foo()
boo_obj = Boo()

print(isinstance(foo_obj, Foo))  # True
print(isinstance(boo_obj, Foo))  # False

# issubclass
class Father:
    pass

class Sub(Father):
    pass

class Foo:
    pass

print(issubclass(Sub, Father))  # True
print(issubclass(Foo, Father))  # False

class Foo:
    def __init__(self, x, y):
        self.x = x
        self.y = y

foo_obj = Foo(10, 20)
# hasattr
# 通过字符串x 判断对象中是否有 x属性
print(hasattr(foo_obj, ‘x‘))  # True
print(hasattr(foo_obj, ‘y‘))  # True
print(hasattr(foo_obj, ‘z‘))  # False

# getattr
res = getattr(foo_obj, ‘x‘)
print(res)  # 10

# 若属性不存在，则返回默认值
res = getattr(foo_obj, ‘z‘, ‘默认值‘)
print(res)  # 默认值

# setattr
setattr(foo_obj,‘x‘,40)
print(getattr(foo_obj,‘x‘)) # 40
# 为foo_obj设置一个属性z，值为30
setattr(foo_obj, ‘z‘, 30)
print(hasattr(foo_obj, ‘z‘))  # True

# delattr
delattr(foo_obj, ‘x‘)
print(hasattr(foo_obj, ‘x‘))  # False

# 反射应用:
class FileControl:

    def run(self):
        while True:
            # 让用户输入上传或下载功能的命令:
            user_input = input(‘请输入 上传(upload) 或 下载(download) 功能:‘).strip()

            # 通过用户输入的字符串判断方法是否存在，然后调用相应的方法
            if hasattr(self, user_input):
                func = getattr(self, user_input)
                func()
            else:
                print(‘输入有误!‘)

    def upload(self):
        print(‘文件正在上传...‘)

    def download(self):
        print(‘文件正在下载...‘)


file_control_obj = FileControl()
file_control_obj.run()

# 代码同上，用来测试反射里面类型变化
class choose:    
    def run(self):
        while True:
            cmd = input(‘请输入命令:‘).strip()
            if hasattr(self,cmd):
                print(getattr(self,cmd))    # 把字符串转化为方法
                # <bound method choose.load of <__main__.choose object at 0x00000000022A5F28>>
                print(type(getattr(self,cmd)))
                # <class ‘method‘>
                getattr(self,cmd)() # 运行方法
            else:
                print(‘输入有误‘)

    def load(self):
        print(‘load‘)
    def down(self):
        print(‘down‘)

obj = choose()
print(type(obj.load))   # <class ‘method‘>
obj.run()