... like your implementation. It is not too hard to get the delitem O(log n) compared to your O(n), see here:
So many people are implementing this kind of data type but do not really care about making as fast as it could be ... IMHO yet another reason to ship a usable implementation with Python.
If you use a linked list instead of Python list, you can even do deletion in O(1). Of course, memory consumption will be higher.