I am trying to create a python nonbinary tree class with methods that will allow me to get specific nodes, and apply other methods to those found nodes.
I have started with code from this very nice example: https://www.youtube.com/watch?v=4r_XR9fUPhQ
I have added a method that accepts a string that corresponds to the node (“/” separated, skipping the root) I am looking for, recursively searches the tree, and in theory, returns the node using “self” so I can apply another method on it.
However, when I return(self) it gives me a nonetype back instead of the node.
Advice on how to fix this, or a suggestion of another way to go if this is a bad way to structure things would be greatly appreciated!
Thanks in Advance.
Note: this is only set up to match on leaves so far, but I can fix that if I can get the darn thing to return the node I want.
Code Below:
class TreeNode:
def __init__(self, data):
self.data = data
self.children = []
self.parent = None
self.forecast = None
def get_level(self):
level = 0
p = self.parent
while p:
level += 1
p = p.parent
return level
def print_tree(self):
spaces = ' ' * self.get_level() * 3
prefix = spaces + "|__" if self.parent else ""
print(prefix + self.data)
if self.children:
for child in self.children:
child.print_tree()
def get_node(self, path):
segs = path.split('/')
sep = "/"
print(self.return_child_names())
if self.children:
for child in self.return_child_names():
if segs[0] == child:
found_child = segs.pop(0)
break
self.children[self.return_child_names().index(found_child)].get_node(sep.join(segs))
else:
print("Found the node!")
print(self)
print(self.data)
return(self)
def return_child_names(self):
return([c.data for c in self.children])
def add_child(self, child):
child.parent = self
self.children.append(child)
def build_product_tree():
root = TreeNode("Electronics")
laptop = TreeNode("Laptop")
laptop.add_child(TreeNode("Mac"))
laptop.add_child(TreeNode("Surface"))
laptop.add_child(TreeNode("Thinkpad"))
cellphone = TreeNode("Cell Phone")
cellphone.add_child(TreeNode("iPhone"))
cellphone.add_child(TreeNode("Google Pixel"))
cellphone.add_child(TreeNode("Vivo"))
tv = TreeNode("TV")
tv.add_child(TreeNode("Samsung"))
tv.add_child(TreeNode("LG"))
root.add_child(laptop)
root.add_child(cellphone)
root.add_child(tv)
root.print_tree()
return(root)
product_tree = build_product_tree()
product_tree.get_node("Laptop/Mac").print_tree()
Answer
The problem is in the function get_node: you are not always returning a value. Notably in the following block there is no return, and therefore the function can return None:
if self.children:
for child in self.return_child_names():
if segs[0] == child:
found_child = segs.pop(0)
break
self.children[self.return_child_names().index(found_child)].get_node(sep.join(segs))
The value you get from the recursive call to get_node is neglected. You should actually return it:
return self.children[self.return_child_names().index(found_child)].get_node(sep.join(segs))