Heap & heapSort

class Heap(object):
    def __init__(self, A):
        self._data = A
        self._size = len(A)
        self._build()

    def _build(self):
        m = (len(self._data) - 1) // 2

        for i in xrange(m, -1, -1):
            self._heapify(i)

    def _heapify(self, i):
        left  = 2*i + 1
        right = 2*i + 2

        if left < self._size and self._data[left] > self._data[i]:
            max = left
        else:
            max = i


        if right < self._size and self._data[right] > self._data[max]:
            max = right

        if max != i:
            t = self._data[max]
            self._data[max] = self._data[i]
            self._data[i] = t

            self._heapify(max)

    def heapSort(self):
        n = len(self._data) - 1
        for i in xrange(n, 0, -1):
            t = self._data[0]
            self._data[0] = self._data[i]
            self._data[i] = t
            self._size -= 1
            self._heapify(0)

heap = Heap([1,5,8,9,4,3,2])
print heap._data

heap.heapSort()
print heap._data