python面向对象笔记

# 定义一个类
class Animal:
    # 私有成员(用_开头的约定为私有成员 - 注：仅仅是君子协定)
    _age = 0

    # 构造函数
    def __init__(self, name):
        # 建议所有私有成员在这里初始化（不管是已定义的，还是"动态"添加的）
        self.name = name  # 动态添加的私有成员
        self._age = 1  # 已经定义好的私有成员

    # 静态方法
    @staticmethod
    def eat():
        print("Animal can eat food")

    # 公有方法
    def to_string(self):
        return "name:" + self.name

    # 私有方法(用_开头的约定为私有方法 - 注：仅仅是君子协定)
    def _some_method(self):
        return "this is a private method of :" + self.name

    # setter示例
    def set_age(self, age):
        if age < 0 or age > 100:
            print("age is invalid!")
        self._age = age

    # getter示例
    def get_age(self):
        return self._age

    def run(self):
        print(self._some_method())
        print("I am running")

    def test(self):
        print("test1")

    # 注：这样会覆盖上面的test(self版本)
    def test(self, hello):
        print("test2:" + hello)


animal = Animal("A new animal")
print(animal.to_string())  # 方法调用
animal.eat()  # 静态方法调用1（不推荐）
Animal.eat()  # 静态方法调用2
print("animal._age=" + str(animal.get_age()))
animal.set_age(10)  # 调用setter
print(animal.get_age())  # 调用getter,输出10
animal.run()  # 公有方法里调用私有方法
animal._age = 30  # 直接修改私有成员(不推荐)
animal._age2 = 40  # 注意：这里实际上给实例animal"动态"添加了一个_age2属性
print(animal.get_age())  # 这里输出的仍然是10
print("_age2:" + str(animal._age2))  # 这里输出的动态添加的_age2属性值
print(animal.test("hi"))
#print(animal.test())  # 这里会报错，因为test(self,hello)这个版本要求hello参数有值
print(animal._some_method())  # 直接调用私有方法(不推荐)

name:A new animal
Animal can eat food
Animal can eat food
animal._age=1
10
this is a private method of :A new animal
I am running
30
_age2:40
test2:hi
None
this is a private method of :A new animal

# 定义一个类
class Calculator:
    # 加法
    def add(self, a=0, b=0, c=0, d=0):
        print("args:", a, b, c, d)
        return int(a) + int(b) + int(c) + int(d)


cal = Calculator()
print(cal.add(1, 2))
print(cal.add(1, 2, 3))
print(cal.add(1, "2", 3, "4"))

print("\n")

cal = Calculator #注意这里，如果漏了()，结果会大不同
print(cal.add(1, 2))

args: 1 2 0 0
3
args: 1 2 3 0
6
args: 1 2 3 4
10


args: 2 0 0 0
2　　

# 定义一个类
class Calculator:
    # 约定：*参数，表示参数个数不限定
    def add(self, *args):
        result = 0
        for arg in args:
            result += int(arg)
        return result


cal = Calculator()
print(cal.add(1, 2, 3))
print(cal.add("1", 2, "3"))

6
6

class Fruit:
    def __init__(self, name):
        print("Fruit constructor...")
        self.name = name

    def to_string(self):
        print("Fruit to_string...")
        return "name:" + self.name

    # 抽象方法
    def get_color(self):
        print("Fruit get_color...")
        raise NotImplementedError


class RedApple(Fruit):
    def __init__(self, name):
        print("Apple constructor...")
        # 调用父类的构造函数
        Fruit.__init__(self, name)

    def get_color(self):
        return self.name + " is red"


fruit = Fruit("unknown")
print(fruit.to_string())
# print(fruit.get_color())  # 报错，因为没实现
print("\n")

redApple = RedApple("red apple")
print(redApple.get_color())
print(redApple.to_string())

print("\n")
print("1、redApple is instance of RedApple ? ", isinstance(redApple, RedApple))
print("2、redApple is instance of Fruit ? ", isinstance(redApple, Fruit))
print("3、fruit is instance of Fruit ? ", isinstance(fruit, Fruit))
print("4、fruit is instance of RedApple ? ", isinstance(fruit, RedApple))
print("5、RedApple is subclass of Fruit ? ", issubclass(RedApple, Fruit))
print("6、Fruit is subclass of Fruit ? ", issubclass(Fruit, Fruit))
print("7、Fruit is subclass of RedApple ? ", issubclass(Fruit, RedApple))

Fruit constructor...
Fruit to_string...
name:unknown


Apple constructor...
Fruit constructor...
red apple is red
Fruit to_string...
name:red apple


1、redApple is instance of RedApple ?  True
2、redApple is instance of Fruit ?  True
3、fruit is instance of Fruit ?  True
4、fruit is instance of RedApple ?  False
5、RedApple is subclass of Fruit ?  True
6、Fruit is subclass of Fruit ?  True
7、Fruit is subclass of RedApple ?  False

class P1:
    def a(self):
        print("P1-a")

    def b(self):
        print("P1-b")

    def x(self):
        print("P1-x")


class P2:
    def a(self):
        print("P2-a")

    def b(self):
        print("P2-b")

    def y(self):
        print("P2-y")


# 多继承示例
class S1(P1, P2):
    def a(self):
        print("S1-a")


class S2(P2, P1):
    def a(self):
        print("S2-a")


s1 = S1()
s1.a()
s1.b()  # P1-b
s1.x()
s1.y()

print("\n")

s2 = S2()
s2.a()
s2.b()  # P2-b
s2.x()
s2.y()

print("\n")

print("s1 isinstance of P1:", isinstance(s1, P1))
print("s1 isinstance of P2:", isinstance(s1, P2))
print("s1 isinstance of S1:", isinstance(s1, S1))
print("s1 isinstance of S2:", isinstance(s1, S2))

S1-a
P1-b
P1-x
P2-y


S2-a
P2-b
P1-x
P2-y


s1 isinstance of P1: True
s1 isinstance of P2: True
s1 isinstance of S1: True
s1 isinstance of S2: False

from abc import *


# 接口示例
class IRun(ABC):
    # 抽象方法
    @abstractmethod
    def run(self):
        pass


class Animal(ABC):
    # 抽象属性
    @property
    @abstractmethod
    def name(self):
        pass


class Dog(Animal, IRun):
    def __init__(self, name):
        self._name = name;

    # 属性的getter
    @property
    def name(self):
        return self._name

    # 属性的setter (注：每个property都会生成一个对应的@xxx.setter)
    @name.setter
    def name(self, value):
        self._name = value

    # 接口的方法实现
    def run(self):
        print(self.name + " is running")


dog1 = Dog("a")
dog1.run()
dog2 = Dog("b")
dog2.run()
print(isinstance(dog1, IRun))
print(id(dog1), id(dog2), id(dog1) == id(dog2))  # 判断2个实例是否相等

a is running
b is running
True
4314753736 4314753792 False