Assign a object to the pointer the node is referring - python-3.4

Question

class BinarySearchTree:
def __init__(self, value=None, left=None, right=None):
self.value = value
self.left = left
self.right = right
def insert(self, value) -> bool:
current_node = self
while current_node is not None:
if current_node.value < value:
current_node = current_node.left
elif current_node.value == value:
return False
elif current_node.value > value:
current_node = current_node.right
# id(current_node) <-- I need to create a object on this
current_node = BinarySearchTree(value) # <--
# id(current_node) <-- This is a new assigned id, but I need the same as the previous id
return True
binary_search_tree = BinarySearchTree(2)
binary_search_tree.insert(5)
print(binary_search_tree.__dict__)
current_node refers to current_node.left or current_node.right.
I need to create a new object and assign it to the pointer the current_node is referring,
but I only create a new object and assign it to a new pointer.

Answer 1

a new assigned id, but I need the same as the previous id
After the loop, as Scott Hunter noted, current_node is None, so the previous id is the “identity” of None, and you surely understand that a new object's id cannot be the same as the id of None. What you could do is modify the loop in a way which allows to refer to the attribute left or right afterwards as needed:
while current_node is not None:
object = current_node # remember the node to be changed
if current_node.value < value:
current_node = current_node.right
name = 'right' # remember the attribute to be changed
elif current_node.value == value:
return False
elif current_node.value > value:
current_node = current_node.left
name = 'left' # remember the attribute to be changed
setattr(object, name, BinarySearchTree(value)) # make the change
Alternatively you could make things a bit more simple by replacing in __init__
self.left = left
self.right = right
with
self.subtree = [left, right]
and the whole body of insert with
if value == self.value: return False
t = 0 if value < self.value else 1
if self.subtree[t]: return self.subtree[t].insert(value)
self.subtree[t] = BinarySearchTree(value)
return True