Conditional to create a new column

Question

I have a pandas data frame and y have 2 columns, A and B. Column A has some null values so I want to create a column C like this, if A have a null value then take the value of B, else take the value of A. I am using this code but it´s not working:

if data['A'] is None: data['C'] = data['B'] else: data['C'] = data['A']

Vivek Kalyanarangan · Accepted Answer · 2021-08-17 16:29:22Z

1

Use fillna -

data['C'] = data['A'].fillna(data['B'])

answered Aug 17, 2021 at 16:29

Vivek Kalyanarangan

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Ossi H. · Accepted Answer · 2021-08-17 17:53:29Z

If you are using the exact sample code, you are missing a Semi-quotation mark on line 2 after C, otherwise you can do this:

Use isnull instead of is None

import pandas as pd data = pd.DataFrame({'A': [1,None], 'B': [3, 4]}) if data['A'].isnull: data['C'] = data['B'] else: data['C'] = data['A'] print (data['C'].values)

Output [3 4]

Here is a link to pandas official doc, DataFrame.isnull

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