Calculating sums of the even- and the odd-indexed numbers

Write a odd_sum function that takes a list or tuple of numbers. It should return a two-element tuple, containing (respectively) the sum of the even-indexed numbers and the sum of the odd-numbered numbers. Example:

>>> odd_even_sum([2,4,6,1,12,3,4])
    (24, 8)
>>> odd_even_sum([0,2,4,6,1,12,3,4])
    (8, 24)
>>> odd_even_sum((1,2,1,2,1,2))
    (3, 6)
>>> odd_even_sum((2,1,2,1,2,1,2))
    (8, 3)
>>> odd_even_sum(())
    (0, 0)
>>> odd_even_sum([])
    (0, 0)