March 2022
Intermediate to advanced
522 pages
13h 52m
Chinese
Content preview from Python语言及其应用（第2版）
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19
第 2 章
数据：类型、值、变量和名称
美名胜于钱财。
——箴言篇
22:1
在底层，计算机中的一切都只是位序列而已（参见附录
A
）
。认识到这一点，意味着我们
能够以任何方式解释这些位，它们既可以是大小和类型（数字、文本字符）各异的数据，
也可以是计算机代码。我们使用
Python
根据不同的目的定义位序列，并将其送返于
CPU
。
先从
Python
的数据
类型
及其包含的
值
开始。然后学习如何将数据描述为
字面值
和
变量
。
2.1 Python
数据皆是对象
可以将计算机的内存想象成一排排的架子。每个内存架子中的一个空栏就是一字节（
8
位）
宽，空栏的编号从
0
（第一个）开始直到结束
。现代计算机具有数十亿字节的内存（千兆
字节），因此，这些架子将填满一间巨大的仓库。
操作系统允许
Python
程序访
问计算机的部分内存。这部分内存用于程序本身的代码以及使
用的数据。操作系统可以确保程序在未经许可的情况下无法读取或写入其他内存位置。
程序会跟踪其内存位置（内存地址）以及其中包含的内容（数据类型）。对于计算机来说，
一切都只是位而已。取决于我们所说的类型，相同的位代表着不同的含义。同样的位模式
也许表示整数
65
或文本字符
A
。
不同的类型可能使用不同数量的位。当你说到一台“
64
位计算机”的时候
，这意味着其使
用
64
位（
8
字节）表示一个整数。
有些语言直接对内存中的这些原始值进行操作，跟踪其大小和类型。
Python
没有选择这种
做法，而是将内存中的各种值（布尔值、整数、浮点数、字符串，甚至大型数据结构、函
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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.