other example BT.py

class _Node:
    __slots__ = '_element','_left','_right'
    
    def __init__(self,element, left = None, right = None) -> None:
        self._element = element
        self._left = left
        self._right = right 
        
class BinaryTree:
    
    def __init__(self):
        self._root = None 
        
    def maketree(self,e,left,right):
        self._root = _Node(e,left._root,right._root)
        
    def inorder(self,troot):
        if troot:
            self.inorder(troot._left)
            print(troot._element,end =' ')
            self.inorder(troot._right)
            
    def preorder(self,troot):
        if troot:
            print(troot._element,end =' ')
            self.preorder(troot._left)
            self.preorder(troot._right)
            
    def postorder(self,troot):
        if troot:
            self.postorder(troot._left)
            self.postorder(troot._right)
            print(troot._element,end =' ')
            
x = BinaryTree()
y = BinaryTree()
z = BinaryTree()
r = BinaryTree()
s = BinaryTree()
t = BinaryTree()
a = BinaryTree()

x.maketree(40,a,a)
y.maketree(60,a,a)
z.maketree(20,x,a)
r.maketree(50,a,y)
s.maketree(30,r,a)
t.maketree(10,z,s)
print("Inorder Traversal")
z.inorder(t._root)
print()

print("Postorder Traversal")
z.postorder(t._root)
print()

print("Preorder Traversal")
z.preorder(t._root)
print()