Need help in IF statement in python

I'm working on a data manipulation task, here is my question I have a data from with 2 columns, column (REPORT_GROUP)has list of names 4 names), there are 12 rows for each of names, so in total there are 48 rows I want to add dates from 1/1/2019 to 12/1/2019 for each of the names in a new column So each name will have 12 month. How to go about writing IF statement for this?