April 2023
Intermediate to advanced
769 pages
25h 16m
Chinese
Content preview from 流畅的Python（第2版）
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394
｜
第
14
章
35
个改善编程与设计的有效方法（中文版）》一书中的一句话：“非尾端类都应设计为抽象
类。”也就是说，
Meyer
建议只有抽象类可以子类化。
如果子类化是为了重用代码，那么想要重用的代码应该放入抽象基类的混入方法中，或者
放入名称可明确表明意图的混入类中。
接下来，从这些建议入手分析
Tkinter
。
14.7.8
Tkinter
的好
、
不好以及令人厌恶的方面
前几节给出的建议，
Tkinter
大都没有采用，
14.7.5
节例外。但是，
Tkinter
做得并不好，因
为使用组合模式把几何管理器集成到
Widget
中或许更好，详见
14.7.1
节。
记住一点，自
1994
年发布的
Python 1.1
起，
Tkinter
就在标准库中了
。
Tkinter
的底层是
Tcl
语言优秀的
GUI
工具包
Tk
。
T
cl/Tk
组合原本不是面向对象的，因此
Tk API
基本上就是一
堆函数。尽管没有使用面向对象方式实现，但是这个工具包的理念极具面向对象思想。
tkinter.Widget
类的文档字符串开头说它是“内部类”。这或许表明，
Widget
应该被定义
为抽象基类。虽然
Widget
自身没有方法，但是它定义了接口。它传达的意思是：“每个
Tkinter
小组件都会提供基本的方法
（
__init__
、
destroy
，以及众多
Tk API
函数），此外
还会提供
3
个
几何管理器中的全部方法。”你可以不同意这是定义接口的好方式（太宽泛
了），但是这样确实能定义接口，
Widget
就把接口“定义”为超类接口的联合。
封装
GUI
应用程序逻辑的
Tk
类继承自
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I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.