Using if then with python pandas

Question

I have a dataset using pandas in python and would like to apply an if-then-else rule for a specific column.

If the there is missing value, then replace it with a specific value taken from another column in the same observation, else do nothing.

My dataset is generated by the code as follow:

results = df2.merge(df1,on="sku", how="left")

The column variable that needs to be filled, if empty is "stock_y". If empty, the value of the column variable "stock_x" should be copied to "stock_y". In the case that stock_y is already filled, the code should skip the observation.

Look into fillna. Ps your post will probably be downvoted if you don't post sample data. — manwithfewneeds
– manwithfewneeds, Commented Sep 22, 2019 at 11:21

Code Different · Accepted Answer · 2019-09-22 11:37:02Z

2

Check out Series.combine_first:

results['stock_y'] = results['stock_y'].combine_first(results['stock_x'])

answered Sep 22, 2019 at 11:37

Code Different

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PineapplePizza · Accepted Answer · 2020-02-06 19:26:40Z

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Implementation with fillna:

results['stock_y'] = results['stock_y'].fillna(results['stock_x'])

answered Feb 6, 2020 at 19:26

PineapplePizza

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