python - Binary Search Tree 'Int object not iterable' -

so i'm new programming , trying make delete function in binary search tree delete on side has highest depth of nodes. however, keep getting error once try run , know simple fix cannot figure out after reading few similar questions on here.

here error get:

c:\python33\python.exe "c:/users/koopt_000/desktop/college/sophomore semester 2/computer science 231/chapter7/test.py" traceback (most recent call last):   file "c:/users/koopt_000/desktop/college/sophomore semester 2/computer science 231/chapter7/test.py", line 10, in <module>     a.delete(tree, 9)   file "c:\users\koopt_000\desktop\college\sophomore semester 2\computer science 231\chapter7\binarysearchtree.py", line 111, in delete     ldepth == max(self.height(root.left)) typeerror: 'int' object not iterable  process finished exit code 1 

here following parts of code starting treenodes, bst(main function), , test code.

 class treenode(object):      def __init__(self, data = none, left=none, right=none):         self.item = data         self.left = left         self.right = right      def __str__(self):         return str(self.item) 

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from treenode import treenode   class bst(object):      #------------------------------------------------------------      def __init__(self):          """create empty binary search tree         post: empty tree created"""          self.root = none         self.size = 0      def delete(self, root, item, ldepth = 0, rdepth = 0 ):          """remove item binary search tree         post: item removed tree"""           if ldepth == 0:             ldepth == max(self.height(root.left))         if rdepth == 0:             rdepth == max(self.height(root.right))          if ldepth > rdepth:             depth = ldepth             print(depth)         elif ldepth < rdepth:             depth = rdepth             print(depth)         else:             depth = ldepth             print(depth)          self.root = self._subtreedelete(root, item, depth)      #------------------------------------------------------------      def _subtreedelete(self, root, item, depth):          if root none:   # empty tree, nothing            return none         if item < root.item:                             # modify left             root.left = self._subtreedelete(root.left, item)         elif item > root.item:                           # modify right             root.right = self._subtreedelete(root.right, item)         else:                                            # delete root             if root.left none:                        # promote right subtree                 root = root.right             elif root.right none:                     # promote left subtree                 root = root.left             else:                 # root node can't deleted, overwrite max of                  #    left subtree , delete max node subtree                 root.item, root.left = self._subtreedelmax(root.left)         return root      #------------------------------------------------------------      def _subtreedelmax(self, root):          if root.right none:           # root max              return root.item, root.left  # return max , promote left subtree         else:             # max in right subtree, recursively find , delete             maxval, root.right = self._subtreedelmax(root.right)             return maxval, root        def height(self, root):         if root none:             return 0         else:             return max(self.height(root.left), self.height(root.right)) + 1 

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from binarysearchtree import bst treenode import treenode  tree = treenode(4, treenode(2, treenode(1), treenode(3)), treenode (7, treenode(6),treenode(9)))   = bst() a._subtreeinsert(tree, 10) a._subtreeinsert(tree, 5) a.delete(tree, 9)  print("pre-order transverse:") print(a.preorder(tree)) print("in-order transverse:") print(a.inorder(tree)) print("post-order transverse:") print(a.postorder(tree))  print("the max depth of tree is,", a.height(tree),"nodes deep.") print("there are,", a.treesize(tree),"nodes in tree.") 

could tell me whats wrong? need work in order make delete function work properly,

the max() function in python takes iterable object, list, in can iterates on find max value.

self.height(root.left) 

is single int, single value not iteratable, throwing error.