Python not defined recursive function?

Question

I'm making a binary tree in Python 3.5.0 and I'm making the insert function for it. But I'm running in a bit of a problem when I call tree_insert inside itself it gives me this error:

  File "D:/MadeUpPath/BinaryTree.py", line 10, in tree_insert
    tree_insert(data, self.left)
NameError: name 'tree_insert' is not defined

class BinaryTree():
    def __init__(self, data):
        self.left = None
        self.right = None
        self.data = data

    def tree_insert(self, data):
        if (data < self.data):
            if (self.left != None):
                tree_insert(data, self.left)
            else:
                self.left = BinaryTree(data)
        else:
            if (self.right != None):
                tree_insert(data, self.right)
            else:
                self.right = BinaryTree(data)

Upon testing further I found out that recursive functions simply don't work. I tried the following code to be sure but gave me the same error:

def factorial(n):
    if n == 0:
        return 1
    else:
        return n * factorial(n - 1)

  File "D:/MadeUpPath/BinaryTree.py", line 23, in factorial
    return n * factorial(n - 1)
NameError: name 'factorial' is not defined

If anyone can point me in the right direction it would be much appreciated :)

Answer 1

tree_insert() is an instance method, call it via self.tree_insert():

class BinaryTree():
    def __init__(self, data):
        self.left = None
        self.right = None
        self.data = data

    def tree_insert(self, data):
        if (data < self.data):
            if (self.left != None):
                self.tree_insert(data, self.left)
            else:
                self.left = BinaryTree(data)
        else:
            if (self.right != None):
                self.tree_insert(data, self.right)
            else:
                self.right = BinaryTree(data)