pandas DataFrame 警告（SettingWithCopyWarning）

Posted 2020-11-22 sxinfo

报警：

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

简单述之：

A为一个dataframe，

B = A[[‘a‘, ‘b‘]]
B[‘a‘] = B[‘a‘] + 1

将会有上面的警告，提示最后一行有问题，但实际上应该修改上一行,为：

B = A.loc[:,[‘a‘,‘b‘]]

详见：

https://www.cnblogs.com/pig-fly/p/7875472.html