import numpy as np

class extensible_array (object):
    def __init__(self, ndims=0, dtype=int, init=None):
        if init is not None:
            self.arr = init
        else:
            self.arr = np.zeros ([0]*ndims, dtype=dtype)

    def __getitem__ (self, indices):
        try:
            return self.arr.__getitem__ (indices)
        except IndexError:
            self.resize ([i+1 for i in indices])
            return self.arr.__getitem__ (indices)

    def __setitem__ (self, indices, value):
        try:
            return self.arr.__setitem__ (indices, value)
        except IndexError:
            self.resize ([i+1 for i in indices])
        return self.arr.__setitem__ (indices, value)

    def resize (self, indices):
        if any ([i > x for x,i in zip (self.arr.shape, indices)]):
            newarr = np.zeros ([max (i,x) for x,i in zip (self.arr.shape, indices)], dtype=self.arr.dtype)
            newarr[[slice(0,i) for i in self.arr.shape]] = self.arr
            self.arr = newarr

    def __iadd__ (self, other):
        maxshape = [max (a,b) for a,b in zip (self.shape, other.shape)]
        self.resize (maxshape)
        self.arr[[slice(0,i) for i in other.shape]] += other
        return self

    def __getattr__(self, name):        # delegate all operations not specifically overridden to base array
        return getattr (self.arr, name)

    def __repr__ (self):
        return self.arr.__repr__()

def test1():
    u = extensible_array (2)
    u[1,1] += 2
    u += u
    return u

if __name__ == '__main__':
    u = test1()