There can be several ways to change the data type of list elements. You can try the following two one-liner pythonic approaches:
>>> a=['aa','1','0','1']
>>> map(int,a[1:])
[1, 0, 1]
>>> [int(s) for s in a[1:]]
[1, 0, 1]
To compute the sum of the list items, you can do one of the followings:
>>> sum(map(int,a[1:]))
2
>>> sum([int(s) for s in a[1:]])
2