Efficient date range overlap calculation in python?

Question

I have two date ranges where each range is determined by a start and end date (obviously, datetime.date() instances). The two ranges can overlap or not. I need the number of

Answer 1

def get_overlap(r1,r2):
    latest_start=max(r1[0],r2[0])
    earliest_end=min(r1[1],r2[1])
    delta=(earliest_end-latest_start).days
    if delta>0:
        return delta+1
    else:
        return 0