March 2022
Intermediate to advanced
522 pages
13h 52m
Chinese
Content preview from Python语言及其应用（第2版）
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.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.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.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.
44
｜
第
4
章
sum = 1 +
^
SyntaxError: invalid syntax
有一个小窍门，如果位于一对圆括号（也可以是方括号或花括号）内部，那么
Python
就不
会抱怨行尾了：
>>> sum = (
... 1 +
... 2 +
... 3 +
... 4)
>>>
>>> sum
10
在第
5
章中你还会看到，成对的三引号可以生成多行字符串。
4.3
使用
if
、
elif
和
else
进行比较
现在，我们终于迈出了第一步，来到了将数据编织成程序的代码结构。第一个例子是下面
这个短小的
Python
程序，它会检查布尔变量
disaster
的值并打印出相应的点评：
>>> disaster = True
>>> if disaster:
... print("Woe!")
... else:
... print("Whee!")
...
Woe!
>>>
if
和
else
是
Python
语句
，负责检查条件（在这里是
disaster
的值）是否为
True
，或者是
否可以被评估为
True
。记住，
print()
是
Python
的内建函数，通常用于在屏幕上打印内容。
如果你之前使用过其他编程语言，那么注意
if
语句在
Python
中是不需要圆
括号的。例如，不用写成
if (disaster == True)
（等量运算符
==
马上就会
讲到）。只需在结尾加上冒号（
:
）即可。如果你有时忘了写冒号（像我一
样 ），
Python
就会报错。
该测试之后的每个
print()
都是缩进的。每级缩进使用了
4
个空格。尽管你可以使用自己 ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
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.