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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28
｜
第
2
章
列表
是值的可变数组，第
7
章会详细介绍
。在这个例子中，
a
和
b
均指向一个包含
3
个整
数的列表：
>>> a = [2, 4, 6]
>>> b = a
>>> a
[2, 4, 6]
>>> b
[2, 4, 6]
列表成员（
a[0]
、
a[1]
和
a[2]
）的作用类似于名称，分别指向值为
2
、
4
和
6
的整数对象。
列表对象会保持其成员的顺序。
通过名称
a
修改第一个列表元素，
b
也会随之发生变化：
>>> a[0] = 99
>>> a
[99, 4, 6]
>>> b
[99, 4, 6]
当第一个列表元素被修改时，它就不再指向值为
2
的对象了，而是指向另一个值为
99
的
新对象。列表的类型依然是
list
，但它的值（列表元素及其顺序）是可变的。
2.11
选个好变量名
他说的是实情，却叫错了名字。
——
Elizabeth Barrett Browning
选一个好变量名的重要性出乎你的意料。在目前很多示例代码中，我使用的是像
a
和
x
这
种用完就扔的名称。在真实程序中，要同时跟踪的变量有很多，你需要在简洁和清晰之间
做出平衡。例如，输入
num_loons
肯定要比
number_of_loons
或
gaviidae_inventory
省事，
但它比
n
更明晰。
2.12
后续内容
数字！它们和你预想的一样令人兴奋。好吧，也许只是没那么糟糕吧。
5
你将看到如何将
Python
作为一个计算器使用，以及一只猫咪如何建立一套数字系统。
2.13
练习
1.
将整数值
99
赋给变量
prince
并打印该变量。
2.
数值
5
是什么类型？
3.
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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.