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Keep getting Attribute Errors with my code any suggestions?
There are two files attatched

from string12 import *
from root import *

def main():
    tree1 = raw_input("enter numbers: ")
    print buildParseTree(tree1)
    

def buildParseTree(fpexp):
    fplist = fpexp.split()
    pStack = Stack()
    eTree = BinaryTree('')
    pStack.push(eTree)
    currentTree = eTree
    for i in fplist:
        if i == '(':
            currentTree.insertLeft('')
            pStack.push(currentTree)
            currentTree = currentTree.getLeftChild()
        elif i not in '+-*/)':
            currentTree.setRootVal(eval(i))
            parent = pStack.pop()
            currentTree = parent
        elif i in '+-*/':
            currentTree.setRootVal(i)
            currentTree.insertRight('')
            pStack.push(currentTree)
            currentTree = currentTree.getRightChild()      
        elif i == ')':
            currentTree = pStack.pop()
        else:
            print "error:  I don't recognize " + i
    return eTree
main()
class BinaryTree:
    def __init__(self,rootObj):
        self.key = rootObj
        self.left = None
        self.right = None

    def insertLeft(self,newNode):
        if self.left == None:
            self.left = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.left = self.left
            self.left = t

    def insertRight(self,newNode):
        if self.right == None:
            self.right = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.right = self.right
            self.right = t

    def getRootVal(root):
        return root[0]
    
    def setRootVal(root,newVal):
        root[0] = newVal
    
    def getLeftChild(root):
        return root[1]
    
    def getRightChild(root):
        return root[2]
class Stack:
    def __init__(self):
        self.items = []

    def isEmpty(self):
        return self.items == []

    def push(self, item):
        self.items.append(item)

    def pop(self):
        return self.items.pop()

    def peek(self):
        return self.items[len(self.items)-1]

    def size(self):
        return len(self.items)
  • 2 Contributors
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  • 10 Hours Discussion Span
  • Latest Post Latest Post by Gribouillis
Member Avatar for Gribouillis

Keep getting Attribute Errors with my code any suggestions?
There are two files attatched

from string12 import *
from root import *

def main():
    tree1 = raw_input("enter numbers: ")
    print buildParseTree(tree1)
    

def buildParseTree(fpexp):
    fplist = fpexp.split()
    pStack = Stack()
    eTree = BinaryTree('')
    pStack.push(eTree)
    currentTree = eTree
    for i in fplist:
        if i == '(':
            currentTree.insertLeft('')
            pStack.push(currentTree)
            currentTree = currentTree.getLeftChild()
        elif i not in '+-*/)':
            currentTree.setRootVal(eval(i))
            parent = pStack.pop()
            currentTree = parent
        elif i in '+-*/':
            currentTree.setRootVal(i)
            currentTree.insertRight('')
            pStack.push(currentTree)
            currentTree = currentTree.getRightChild()      
        elif i == ')':
            currentTree = pStack.pop()
        else:
            print "error:  I don't recognize " + i
    return eTree
main()

I got something by replacing root.py with

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

    def insertLeft(self,newNode):
        if self.left == None:
            self.left = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.left = self.left
            self.left = t

    def insertRight(self,newNode):
        if self.right == None:
            self.right = BinaryTree(newNode)
        else:
            t = BinaryTree(newNode)
            t.right = self.right
            self.right = t

    def getRootVal(root): # accessor functions are java-ic and not very pythonic.
        return root.key
    
    def setRootVal(root,newVal):
        root.key = newVal
    
    def getLeftChild(root):
        return root.left
    
    def getRightChild(root):
        return root.right

""" Result of main -->
enter numbers: ( 3 * 5 + 7 ) - 4
<root.BinaryTree instance at 0x7f08309c2170>
"""

Note that specialized modules exist to parse arithmetic expressions, and languages in general. Also this snippet could draw your binary tree http://www.daniweb.com/code/snippet323792.html .

Edited by Gribouillis because: n/a
Member Avatar for Gribouillis

With the fastgraph snippet above, I replaced your call to main() by

from fastgraph import graph
import webbrowser as web

def links(tree):
    for n in (tree.left, tree.right):
        if n is not None:
            yield tree, n
            for link in links(n):
                yield link

def label(tree):
    return repr(tree.key)

def show(tree, filename="tree.png"):
    g = graph(links(tree), label, directed=True)
    g.draw(filename, prog = 'dot')
    web.open(filename)


if __name__ == "__main__":
    t = buildParseTree("( 3 * 5 + 7 ) - 4")
    show(t)

This pops up a window showing the tree. This tree is probably not what you are expecting, so there are still errors in your program. Remark that fastgraph cannot distinguish left from right.

tree.png 4.1 KB
Edited by Gribouillis because: n/a
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