class Node:

    def __init__(self,left,value,right):
        self.left = left
        self.value = value
        self.right = right

    def insert(self,x):
        if x < self.value:
            if self.left == None:
                self.left = Node(None,x,None)
                return True
            else:
                return self.left.insert(x) 
        elif x > self.value:
            if self.right == None:
                self.right = Node(None,x,None)
                return True
            else:
                return self.right.insert(x)
        else:
            return False
        
    def __str__(self):
        if self.left != None:
            if self.right != None:
                return str(self.left) + "," + str(self.value) + "," + str(self.right)
            else:
                return str(self.left) + "," + str(self.value)
        else:
            if self.right != None:
                return str(self.value) + "," + str(self.right)
            else:
                return str(self.value)

class BST:

    def __init__(self):
        self.root = None
    
    def empty(self):
        return self.root == None

    def insert(self,x):
        if self.empty():
            self.root = Node(None,x,None)
        else:
            self.root.insert(x)

    def __str__(self):
        if self.empty():
            return "{ }"
        else:
            return "{" + str(self.root) + "}"

t = BST()
t.insert(50)
t.insert(30)
t.insert(60)
print(t)

{30,50,60}