April 2023
Intermediate to advanced
769 pages
25h 16m
Chinese
Content preview from 流畅的Python（第2版）
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646
｜
第
22
章
➎
实现为内置函数
dir()
提供支持的
__dir__
方法，进而支持在
Python
标准控制台，以及
IPython
、
Jupyter
Notebook
等中自动补全。这个方法的代码很简单，将基于
self.__data
中的键实现递归自动补全，因为
__getattr__
方法能即时构建
FrozenJSON
实例——方便
采用交互方式探索数据。
➏
这是一个备选构造方法，是
@classmethod
装饰器的常见用途。
➐
如果
obj
是一个映射，那么就构建一个
FrozenJSON
对象。这里利用了
大鹅类型
（详见
13.5
节
）。
➑
如果是一个
MutableSequence
对象，则必然是列表，
6
因此，把
obj
中的每一项递归都传
给
.build()
方法，构建一个列表。
➒
如果既不是字典也不是列表，那么原封不动返回项。
FrozenJSON
实例的私有实例属性
__data
存储在
_FrozenJSON__data
名下（详见
11.10
节 ）。
尝试通过其他名称获取属性将触发
__getattr__
方法。这个方法会先查看
self.__data
字
典有没有指定名称的属性（不是键），这样
FrozenJSON
实例便可以处理
dict
的方法，例
如把
items
方法委托给
self.__data.items()
。如果
self.__data
没有指定名称的属性，那
么
__getattr__
方法就会以那个名称为键，从
self.__data
中获取一项，传给
FrozenJSON.
build
方法。这样便能深入
JSON
数据的嵌套结构，使用类方法 ...
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I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
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.