January 2023
Intermediate to advanced
458 pages
14h 16m
Chinese
Content preview from 可编程网络自动化
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在网络场景中学习
Python
｜
79
4.3.3
学习使用布尔值
布尔对象（在
Python
中也称为
bool
类型的对象）的用法相当直观。先来通过
真值表
（参
见表
4-2
）了解一下布尔逻辑的基础。
表 4-2：布尔真值表
A B A and B A or B Not A
False False False False True
False True False True True
True False False True False
True True True True False
注意，表中所有的值不是
True
，就是
False
。这是因为在布尔逻辑中，所有的值都被归结
为
True
或
False
。这实际上使得布尔逻辑很容易理解。
由于布尔值只能为
True
或
False
，因此所有表达式的求值结果要么为
True
，要么为
False
。
从表中可以看出，“
A
and B
”要想为
True
，
A
和
B
必须均为
True
。如果
A
或
B
其中之一
为
True
，则“
A or B
”为
True
。如果对布尔值求否（
NOT
），则会得到相反的值。因此，
“
NOT
False
”的值为
True
，“
NOT True
”的值为
False
。
从
Python
的角度来
看也是一样。我们仍然只有两个布尔值：
True
和
False
。要想在
Python
中将其中一个值赋给变量，必须照原样输入（首字母大写，不能加引号）。
>>> exists = True
>>>
>>> exists
True
>>>
>>> exists = true
Traceback (most recent ...
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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.