l1 = [(1, 100), (2, 1000), (4, 1500), (5, 5400), (7, 7800)]
l2 = [(1, 20), (2, 400), (3, 240), (4, 500), (5, 100), (6, 27)]
s1 = pd.Series(dict(l1))
s2 = pd.Series(dict(l2))
Join two timelines / list of tuples