类与对象基础操作（类属性，私有，继承，强制访问）

import math
#form ex_point import Point #从ex_point中引用Point类
class Point:
    counter = 0 #类属性(公共的)
    def __init__(self,x=0,y=0,pwd="pass"):#初始化+默认值
        self.x = x
        self.y = y
        self.__pwd = pwd # 私有属性
        Point.counter += 1
    def __prtpass(self):# 私有方法
        print(self.__pwd)

class Circle(Point):#继承
    def __init__(self,x=0,y=0,r=0):
        super().__init__(x,y)
        self.r = r
    def Area(self):#面积
        return math.pi * self.r ** 2
    def Perimeter(self):#周长
        return 2 * math.pi * self.r

class Cylinder(Circle):#继承
    def __init__(self,x=0,y=0,r=0,h=0):
        super().__init__(x,y,r)
        self.h = h
    def Area(self):#表面积(同名方法覆盖)
        return super.Area() * 2 + super.Perimeter() * self.h
    def Volume(self):#体积
        return super.Area() * self.h

aPoint = Point(1,0)
aPoint.x = 100
bPoint = Point()
print(bPoint.x)#输出0

print(Point.counter)#输出2
print(aPoint._Point__pwd)#强制访问私有属性aPoint.__pwd
aPoint._Point__prtpass()#强制访问私有方法aPoint.__prtpass()

aCylinder = Cylinder()

定义矩形和正方形类，添加绘图方法，使用继承

import turtle
class Rectangle:#矩形
    def __init__(self,x=0,y=0,long=0,wide=0):
        self.x = x
        self.y = y
        self.long = long
        self.wide = wide
    def draw(self):
        turtle.setup(400,400,200,200)
        turtle.penup()
        turtle.goto(self.x,self.y)
        turtle.pendown()
        turtle.seth(360)
        turtle.fd(self.long)
        turtle.seth(270)
        turtle.fd(self.wide)
        turtle.seth(180)
        turtle.fd(self.long)
        turtle.seth(90)
        turtle.fd(self.wide)
        turtle.penup()

class Square(Rectangle):
    def __init__(self,x=0,y=0,long=0):
        super().__init__(x,y,long,long)

aRectangle = Rectangle(-60,40,90,30)
aRectangle.draw()
aSquare = Square(0,0,60)
aSquare.draw()
bSquare = Square(-40,-30,30)
bSquare.draw()
turtle.done()#暂停程序,停止画笔绘制,但绘图窗体不关闭