文档介绍：第五章面向对象与图形编程 1 overview ? Have you noticed the dot notation with the file variable? () ? This is different than other functions that act on a variable, like abs(x), not (). ? In Python, files are objects , meaning that the data and operations bined . The operations, called methods , are invoked using this dot notation. ? Strings and lists are also objects . More on this later! 2 outline § 面向对象的编程§ 图形编程§ 应用图形对象§ 图形应用例子§ 坐标的选择§ 交互图形§ 图形模块资料 3 outline § 面向对象的编程§ 图形编程§ 应用图形对象§ 图形应用例子§ 坐标的选择§ 图形交互界面§ 图形模块资料 4 数据与操作:面向对象观点?对象( Object ):集数据与操作于一身。对象知道一些信息?对象能对那些信息进行处理?计算:向对象发出请求操作的消息。?主动的数据类型?面向对象( Object-Oriented ):软件系统由各种对象组成,对象之间通过消息进行交互。?现代软件系统几乎都是 OO 设计和实现。 5 OO 基本概念?类( class ):描述同类对象的共性?包含的数据?任何类型的数据,甚至可以是对其他对象的引用.?能执行的操作(方法) ?对象( object ):类的实例( instance )?同类的不同对象可有不同的数据值(实例变量),但能执行的操作是一样的?创建对象:使用类的构造器( constructor ). <类名>(< 参量 1>,< 参量 2>, …) ?消息:请求对象执行它的方法.<对象>.< 方法名>(< 参量 1>,< 参量 2>, …) 6 ? Suppose the graphics processing system. ? There are many kinds of objects: ? Window, Image, Line, Oval, Pixmap ? Point, Polygon, Rectangle, Text ? Each point is an object, for an example. Simple Graphics Programming 7 ? Each point object would contain data like: ? x? Y ? and several operations like: ? draw ? getX ? getY ? move ? undraw ?… Simple Graphics Programming 89 Simple Graphics Programming ? This chapter uses the library supplied with the supplemental materials. ? Two location choices ? In Python ’ s Lib directory with other libraries ? In the same folder as your graphics program 10 Simple Graphics Programming ? Since this is a library, we need to import the mands >>> import graphics ? A graphics window is a place on the screen where the graphics will appear. >>> win = () ? mand creates a new window titled “ Graphics Window. ”