[Tutor] Tree that doesn't grow

[Md. Zahar Othman]

I'm a newbie trying to convert my old Pascal tree program - pointer
implementation to python OOP

The program seem to run but unable to disp the required result.

The method _insert is based on pascal procedure.

Why the method does not work ?

=============================
class binary_tree:

    def __init__(self):
        self.tree=None

    def insert (self,key):
        if self.tree:
            self._insert(self.tree,key)
        else:
            self.tree = node(key)

    def _insert (self,tree,key):
        if  tree==None:
            tree = node(key)
        elif key < tree.key:
            self._insert(tree.left,key)
        elif key > tree.key:
            self._insert(tree.right,key)


class node:
   def __init__(self,key):
        self.key=key
        self.left=None
        self.right=None



t1=binary_tree()
t1.insert(14)
t1.insert(6)
t1.insert(3)


t1.tree.left.key  # error
t1.tree.left.left.key #error



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