解析树ParseTree

from mystack import Stack
from myTree import BinaryTree
import operator

def ParseTree(fp):
    fplist = fp.split()
    fpstack = Stack()
    fptree = BinaryTree('')
    fpstack.push(fptree)
    cur_tree = fptree

    for i in fplist:
        if i == '(':
            cur_tree.insertLeft('')
            fpstack.push(cur_tree)
            cur_tree = cur_tree.getLeftChild()
        elif i not in '+-*/)':
            cur_tree.setRootVal(int(i))
            cur_tree = fpstack.pop()
        elif i in '+-*/':
            cur_tree.setRootVal(i)
            cur_tree.insertRight('')
            fpstack.push(cur_tree)
            cur_tree = cur_tree.getRightChild()
        elif i == ')':
            cur_tree = fpstack.pop()
        else:
            raise ValueError(f'Unknown Character : {i}')

    return fptree


def evaluate(fptree):
    operator_dict = {'+':operator.add, '-':operator.sub, '*':operator.mul, '/':operator.truediv}
    leftchild = fptree.getLeftChild()
    rightchild = fptree.getRightChild()
    if leftchild and rightchild:
        func = operator_dict[fptree.getRootVal()]
        result = func(evaluate(leftchild), evaluate(rightchild))
        return result
    else:
        return fptree.getRootVal()

def printexp(tree):
    s = ''
    if tree:
        if tree.getLeftChild():
            s = '(' + printexp(tree.getLeftChild())
        else:
            s = printexp(tree.getLeftChild())
        s = s + str(tree.getRootVal())
        if tree.getRightChild():
            s = s + printexp(tree.getRightChild()) + ')'
        else:
            s = s + printexp(tree.getRightChild())
    return s


if __name__ == '__main__':
    tree = ParseTree('( 9 - ( 8 / 2 )')
    result = evaluate(tree)
    print(result)
    print(printexp(tree))

输出：

5.0
(9-(8/2))