convert list to tree python

1def normalize(tree, row=0, col=0):
2    try:
3        node = tree[row][col]
4        left  = normalize(tree, row+1, col*2)
5        right = normalize(tree, row+1, col*2+1)
6        return [node, left, right] if left or right else [node]
7    except:
8        return None # child index does not exist