Dynamic Composite key and Make New Column in DataFrame

HI Guys,

I have one requirement in which i am extracting Data
Say having Columns, Column1,Column2,Column3,Clumn4
so i want to make dynamic composite key… Say i want to create a Composite key of
Column1 and Column2 , it would be new column in my dataframe with values of Column1 and Column2
please anyone suggest how i can do that? Composite key could me more than two columns… so no hard code only dynamic way to achieve it… better to use it from any Config file or Input Parameter.

Pls suggest…