binary_expression_tree_evaluate.py

def evaluate(self, node=None) -> float:
      """
      Calculate this tree expression recursively

      Args:
          node(BinaryTreeNode): starts at the root node
      """
      # initialize

      if node is None:
          node = self.root

      # empty tree
      if node is None:
          return 0

      # check if we are at the leaf, it means it is a operand
      if node.is_leaf():
          node.value = float(node.data)
          val = float(node.data)

          return val

      left_value = self.evaluate(node.left)
      right_value = self.evaluate(node.right)

      # addition
      if node.data == "+":

          return left_value + right_value
      # subtraction
      elif node.data == "-":

          print(f"node value: {node.value}")
          return left_value - right_value
      # division
      elif node.data == "/":
          return left_value / right_value
      # multiplication
      elif node.data == "*":
          return left_value * right_value
      # power
      else:
          return left_value ** right_value