How to choose a value from two columns (First and Second) to subtract from another column (Third), based on condition?

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There are 4 columns in total.

VALUE_DIFF is the calculated value. This is based on if column "SECOND" has a value greater than 0, then subtract column value from "SECOND" and "BASE_COLUMN" [ SECOND – BASE_COLUMN]. If column "SECOND" is 0 then subtract column value from "FRIST" and "BASE COLUMN" [FIRST – BASED_COLUMN]

Wondering how can Pandas execute with this condition?

>Solution :

Use numpy.where:

df['DIFF'] = np.where(df['SECOND'].gt(0), df['SECOND'], df['FIRST']) - df['BASE_COLUMN']

What is same like:

df['DIFF'] = np.where(df['SECOND'].gt(0), 
                      df['SECOND']- df['BASE_COLUMN'], 
                      df['FIRST']- df['BASE_COLUMN'])