python-访问二叉树的最大递归错误

我是一名 Python 新手，试图创建一个计算器程序，该程序采用后缀方程返回一个二叉树堆栈对象，然后使用下面的代码格式返回一个中序方程。我的二进制类和树函数似乎正在工作并返回值。但是当使用 inorder 函数时，我得到重复的最大递归错误。任何帮助，将不胜感激！工作二进制类，但以防万一您需要以下代码中调用的函数的上下文：

输入 make_tree: '5 2 3 * +'.split() 我想要返回的内容: (5+(2*3))

class BinaryTree:

    def __init__(self,rootObj):
        self.key = rootObj
        self.leftChild = None
        self.rightChild = None
    def insertLeft(self,newNode):
        if self.leftChild == None:
            self.leftChild = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.leftChild = self.leftChild
            self.leftChild = t
    def insertRight(self,newNode):
        if self.rightChild == None:
            self.rightChild = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.rightChild = self.rightChild
            self.rightChild = t
    def getRightChild(self):
        return self.rightChild
    def getLeftChild(self):
        return self.leftChild
    def setRootVal(self,obj):
        self.key = obj
    def getRootVal(self):
        return self.key
    def __str__(self):
        s = f"{self.key}"
        if self.leftChild != None:
            s += str(self.leftChild)
        if self.rightChild != None:
            s += str(self.rightChild)
        return s

     def make_tree(postfix):
        stack = Stack()
        IsOperator = '+/*-'
        # Traverse through every character of input expression
        kiln = ''.join(postfix)
        for char in kiln:
            # if operand, simply push into stack
            if char not in IsOperator:
                t = BinaryTree(char)
                stack.items.append(t)
                # Operator
            else:
                # Pop two top nodes
                t = BinaryTree(char)
                t1 = stack.pop()
                t2 = stack.pop()

                # make them children
                t.rightChild = t1
                t.leftChild = t2

                # Add this subexpression to stack
                stack.items.append(t)

                # Only element  will be the root of expression tree
        return t

    def __str__(self):
        return ExpTree.inorder(self) ```

My Binary Tree creator is working well but when trying to preorder I am getting errors.

def inorder(self):
    stack = Stack()
    b = BinaryTree
    e = ExpTree
    if tree != []:
        e.inorder(b.getLeftChild(tree))
        print(b.getRootVal(tree))
        e.inorder(b.getRightChild(tree))