Tree insertion and variable referencing

[hshivaraj]

Hey all!
This is probably very basic for some people , but i really cant get my head around this.

The code below performs binary tree insertion. The thing i cant understand is, you'll notice in the _insert function return root. I really dont see the point of that return. However with out that return root. The tree doesn't parse. But however in the calling function insert i dont assign that returned value from _insert to anything. Yet its required. Please help me understand this?

 def insert(self, val): if self.root is None: self.root = Node(val) else: self._insert(self.root, val) def _insert(self, root, val): print(id(root)) if root is None: return Node(val) if val <= root.val: root.left = self._insert(root.left, val) else: root.right = self._insert(root.right, val) return root

[Windspar]

because it recursive function. root.left and root.right need a node.

root.left = self._insert(root.left, val) # need the return

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I believe it to be. None is not a reference variable.

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you could also do this.

class Root:	def __init__(self):	self.root = None	def insert(self, val, root='self'):	if root == 'self':	self.root = self.insert(val, self.root)	elif root is None:	return Node(val)	elif val <= root.value:	root.left = self.insert(val, root.left)	else:	root.right = self.insert(val, root.right)	return root

[hshivaraj]

def insert(self, val, root='self'):[b][/b]

Clever - I didn't know you can do that. Assign self as default argument as a string.

[Windspar]

'self' is just a string. This just check it.

def insert(self, val, root='self'): if root == 'self': self.root = self.insert(val, self.root)

As long as root is not None or a Node. You can have it be anything else.

def insert(self, val, root=True): if root is True: self.root = self.insert(val, self.root)