返回信息流看了文档大概理解为在我这个场景下用df['']和df.loc[:,''] ，是一样的？
http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
https://stackoverflow.com/questions/20625582/how-to-deal-with-settingwithcopywarning-in-pandas
```python
import pandas as pd
df = pd.DataFrame({'a':[1,2,3,'None',4],'b':[4,5,6,7,'None']})
df2 = df[(df['a'] != 'None') & (df['b'] != 'None')]
df2['c'] = df2['a'] + df2['b']
df2
```
/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/site-packages/ipykernel_launcher.py:1: SettingWithCopyWarning:
A value is trying to be set on a copy of a slice from a DataFrame.
Try using .loc[row_indexer,col_indexer] = value instead
See the caveats in the documentation: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
这是一条镜像帖。来源：北邮人论坛 / python / #23204同步于 2018/12/18
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Python机器人发帖
【问题】pandas的DataFrame的SettingWithCopyWarning
qidi
2018/12/18镜像同步3 回复
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3 条回复
楼上正解，不copy的话更改df2会影响df的值
【 在 qidi (lastwhisper) 的大作中提到: 】
: 看了文档大概理解为在我这个场景下用df['']和df.loc[:,''] ，是一样的？
: http://pandas.pydata.org/pandas-docs/stable/indexing.html#indexing-view-versus-copy
: ...................