July 2017
Intermediate to advanced
398 pages
11h 54m
Chinese
Content preview from Python数据处理
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156
｜
第
8
章
➍
用到了
writer
对象的
writerow
方法，将一个可迭代对象转换成一行逗号分隔的数据。本
行代码写入的是标题行。
➎
利用列表生成式提取出所有回答（元组的第二个元素）。
➏
将利用列表生成式创建的所有列表或回答写入
CSV
数据文件。
这里我们用到了学过的语法，也用到了一些新语法。我们已经学过如何用
with...as
将简
单函数的返回值赋值给一个变量名。这里我们希望将打开的文件赋值给
new_csv_file
变
量。这种语法通常用于文件和其他
I/O
对象，因为
Python
执行完
with
代码块中的代码之
后，它会自动关闭文件，这很棒！
此外，代码中我们用到了
CSV writer
对象，与
CSV reader
对象的用法类似。
writerow
可以
将包含所有数据列的列表写入到
CSV
文件中。
writerow
方法接受一个可迭代对象，所以一定要传入一个列表或元组。如果
你传入一个字符串，那么看到一些有趣的
CSV
（“
l,i,k,e, ,t,h,i,s
”）时不要惊讶。
我们还用到了列表生成式来创建标题列表和回答列表。由于我们不需要用这个函数生成一
个新对象或修改过的对象，所以没有返回任何值。这个函数可以帮我们复习目前学过的许
多概念。
如果你想用其他方法来保存数据，可以参考第
6
章给出的关于保存数据的建议。保存完清
洗过的数据之后，你可以继续进行后面的清洗过程，并对数据进行分析。
8.3
找到适合项目的数据清洗方法
根据数据的可靠性，以及你分析数据的频率，你可以选择一种完全不同的数据清洗方式。
如果你要处理的数据是非常杂乱的，或者有许多不同的来源，你可能无法准确地将清洗过 ...
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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.