I have the following dataframe df:
Customer_ID | 2015 | 2016 |2017 | Year_joined_mailing
ABC 5 6 10 2015
BCD 6 7 3 2016
DEF 10 4 5 2017
GHI 8 7 10 2016
I would like to look up the value of the customer in the year they joined the mailing list and save it in a new column.
Output would be:
Customer_ID | 2015 | 2016 |2017 | Year_joined_mailing | Purchases_1st_year
ABC 5 6 10 2015 5
BCD 6 7 3 2016 7
DEF 10 4 5 2017 5
GHI 8 9 10 2016 9
I have found some solutions for match vlookup in python, but none that would use the headers of other columns.