I originally implemented this as a wrapper class around a list, but I was annoyed by the number of operator() methods I needed to provide, so I had a go at simply subclassing list. This is my test code:

    class CleverList(list):

        def __add__(self, other):
            copy = self[:]
            for i in range(len(self)):
                copy[i] += other[i]
            return copy

        def __sub__(self, other):
            copy = self[:]
            for i in range(len(self)):
                copy[i] -= other[i]
            return copy

        def __iadd__(self, other):
            for i in range(len(self)):
                self[i] += other[i]
            return self

        def __isub__(self, other):
            for i in range(len(self)):
                self[i] -= other[i]
             return self

    a = CleverList([0, 1])
    b = CleverList([3, 4])
    print('CleverList does vector arith: a, b, a+b, a-b = ', a, b, a+b, a-b)

    c = a[:]
    print('clone test: e = a[:]: a, e = ', a, c)

    c += a
    print('OOPS: augmented addition: c += a: a, c = ', a, c)

    c -= b         
    print('OOPS: augmented subtraction: c -= b: b, c, a = ', b, c, a)

Normal addition and subtraction work in the expected manner, but there are problems with the augmented addition and subtraction. Here is the output:

    >>> 
    CleverList does vector arith: a, b, a+b, a-b =  [0, 1] [3, 4] [3, 5] [-3, -3]
    clone test: e = a[:]: a, e =  [0, 1] [0, 1]
    OOPS: augmented addition: c += a: a, c =  [0, 1] [0, 1, 0, 1]
    Traceback (most recent call last):
      File "/home/bob/Documents/Python/listTest.py", line 35, in <module>
        c -= b
    TypeError: unsupported operand type(s) for -=: 'list' and 'CleverList'
    >>> 

Is there a neat and simple way to get augmented operators working in this example?