Print preorder traversal of a tree given its inorder and postorder traversals

printPreOrder.py

def search(inorder, instart, inend, key):
    for i in range(instart, inend+1):
        if inorder[i] == key:
            return i
    return None

def printPre(inorder, postorder, instart, inend, poststart, postend):
    if instart > inend or poststart > postend:
        return None

    print postorder[postend],

    k = search(inorder, instart, inend, postorder[postend])

    printPre(inorder, postorder,
             instart, k-1,
             poststart, poststart + k - instart - 1)

    printPre(inorder, postorder,
             k+1, inend,
             poststart + k - instart, postend-1)


inorderarr = [1,2,3,4,5,6,7,8,9,10,11,12]
postorderarr = [1,2,4,3,7,6,5,10,12,11,9,8]

printPre(inorderarr, postorderarr, 0, 11, 0, 11)