how to store the indices into one variable : sub = ['great to have','good to have']

my_string =''' 
*** Strong skills in these can make up for lack of experience in one or two critical areas
Great To Have: 
- DevExpress Experience (in Angular 2+ or AngularJS)
- Strong DBD understanding and experience (set-based artifact design, performance tuning, modeling)
 '''
 
s =""    
for i in sub:
    ii = my_string.lower().find(i)
    my_string[ii:]

how to store the indexes into s variable
