April 2023
Intermediate to advanced
769 pages
25h 16m
Chinese
Content preview from 流畅的Python（第2版）
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接口、协议和抽象基类
｜
367
➊
如果希望衍生的协议可在运行时检查，则必须再次应用这个装饰器，因为该装饰器的行
为不被继承。
21
➋
每个协议都必须明确把
typing.Protocol
列出来，作为基类。另外，再列出要扩展的协
议。这与
Python
中的继承不是一回事。
22
➌
现在是符合“常规”的面向对象编程方式了：只需要声明衍生协议新增的方法。
pick
方法的声明继承自
RandomPicker
。
本章对静态协议的定义和使用就讨论到这里了。
最后，再讲一下数值抽象基类，以及取而代之的数值协议。
13.6.8
numbers
模块中的抽象基类和
Numeric
协议
“论数字塔的倒下”一节讲过，标准库中
numbers
包内的抽象基类可用于做运行时类型检查。
如果想检查是不是整数，可以使用
isinstance(x, numbers.Integral)
。
int
、
bool
（
int
的子类），以及外部库中注册为
numbers
包中某个抽象基类的虚拟子类的整数类型，都
能通过这个测试。例如，
NumPy
提
供了
21
个整数类型，另外还有注册为
numbers.Real
的虚拟子类的多个浮点数类型，以及注册为
numbers.Complex
的虚拟子类的不同位宽度
（
bit width
）的复数。
有点儿奇怪的是，
decimal.Decimal
没有注册为
numbers.Real
的虚拟子类。原因
也很好理解，如果在程序中需要使用
Decimal
提供的精度，那么你肯定不想与
精度低的浮点数混淆。
可惜，
numbers
包定义的数字塔不是为静态类型检查设计的 ...
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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.