熊猫 - 创建一个新专栏

Question

I have always made new columns in pandas using the following:

df['new_column'] = value

I am using this method, however, am receiving the warning for setting a copy.

What is the way to make a new column without creating a copy?

Answer 1

Try using

df.loc[:,'new column'] = value

As piRSquared comments, df is probably a copy of another DataFrame and when you set values to df it probably incurs in what is called chain indexing . Refer to pandas docs for further information.