July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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24
｜
第
2
章
–
删除列表的最后一个元素
–
列表重新排列
–
列表排序
•
字典
–
增加一个键
/
值对
–
将指定的键设置为新的值
–
利用键查找值
在上面这个列表中我们故意没有提到变量。变量能做的事情取决于它包含的
数据。比如说，如果变量是一个字符串，那么它可以做所有字符串能做的事
情。如果变量是一个列表，那么它可以做只有列表才能做的各种事情。
把数据类型看作名词，把它们能做的事情看作动词。在大多数情况下，数据类型能做的事
情被称为
方法
（
method
）。想要访问数据类型的方法，或者说让数据类型做一些事情，你
可以用点号（
.
）。比如说，如果你将一个字符串赋值给名为
foo
的变量，你可以输入
foo.
strip()
来调用该字符串的
strip
方法。我们来看一下其中一些方法的作用。
在调用字符串的方法时，它们的行为是
Python
默认库的一部分（类似于手
机上预装的默认应用），所有
Python
版本共享这一默认库。在每一台运行
Python
的计算机上都可以调用这些方法，因此每一个
Python
字符串都可以
共享相同的方法（就像每一台手机都可以打电话，每一台苹果手机都可以发
送
iMessage
一样）。
Python
标准库（也叫作
stdlib
，
https://docs.python.org/2/
library/
）中包含了大量的内置方法和基本数据类型，其中包括你正在使用的
Python
数据类型。
2.3.1
字符串方法
：
字符串能做什么
回头看最开始定义的变量
filename
。我们开始时用
filename = 'budget.csv'
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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.