Binary Trees Imp | Python Fiddle

''' Binary Trees:
One method: using lists of lists, e.g. a_tree = [root, [left child, child, child][right]]
List implementation: insert_rightt = creates a whole nother tree (recursive)'''

class ListBinaryTree: #list just one implementation
    
    def __init__(self, value):
        self.node = [value, None, None]
        
    def __str__: #used by print()
        n = self.node
        return '[' + n[0] + ',' + str(n[1]) + ',' + str(n[2]) + ']' #is recursive, str being called
    																#prints all children of all nodes
        															#works through recurisvley
            
#eg print(tree_obj) = [59, [4, [7, None, None],None], [6, [5, None, None], [2, None, None]]]

class RefBinaryTree: #storing links, like linked list
    def __init__(self, data): #each node contains links to left and right child
        self.data = data
        self.left = None
        self.right = None
    
    def insert_left(self, data): #creates a new node with data, inserts binary tree object
        t = RefBinaryTree(data)
        if self.left == None: #if no pointer make new
        	self.left = t
        else: 
            t.left = self.left #points old left child to new left child
            self.left = t
    
    def create_string(self, indent): #55---+
  	    info = data
        if there is a left child:
            add to info, add the (l) and newline, and call again with increased indent
        same for right child:
            same
        return the info
        #(l)   4---+
        #(l)         5 ---+
        #(r)   6---+
        #recursive, each call increases indent
        #if r = None, r = False, if not None, r = True
        
    def get_node_sum(self):
        sums = 0
        sums = self.key
        if self == None: #wont work of tree = None
            return 0
        if self.left:
            sums += get_node_sum(self.left)
        get_node_sum(self.left)
        sums += self.get_value()
        
        #python can set defaults for argument e.g. def foo(x,y,z=2,a=None) named parameters
        
        
        return sums

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