Implement LeafNode and InteriorNode classes for the expression tree as discussed on this pageUse this template: Please don't change any function namesAdd any methods if necesssaryTODO: Remove the pass statements and implement the methods. '''class LeafNode:def __init__(self, data):self.data = datadef postfix(self):return str(self)def __str__(self):return str(self.data)def prefix(self):passdef infix(self):passdef value(self):return self.dataclass InteriorNode:def __init__(self, op, left_op, right_op):self.op = opself.left_op = left_opself.right_op = right_opdef postfix(self):return self.left_op.postfix() + " " + self.right_op.postfix() + " " + self.opdef prefix(self):passdef infix(self):passdef value(self):passif __name__ == "__main__":# TODO: (Optional) your test code here.a = LeafNode(4)b = InteriorNode('+', LeafNode(2), LeafNode(3))c = InteriorNode('*', a, b)c = InteriorNode('-', c, b) 316The constructor for Leaf Node expects an integer as an argument, whereas the con-structor for Interior Node expects a character-based operator symbol and two othernodes as arguments.Here is a short tester program that illustrates the use of the node classes:from expressiontree import Leaf Node, InteriorNodea = Leaf Node (4)bInteriorNode('+',Leaf Node (2), Leaf Node (3))c = InteriorNode('*',a, b)c = InteriorNode('-', c, b)=print("Expect ((4* (2+3)) - (2+3)):", c.infix())print("Expect - *4 +23+23:", c.prefix())print("Expect 4 2 3+*23 + -:", c.postfix())print("Expect 15:", c.value())You now develop one of the traversal methods for both classes and leave the others asexercises for you. The method postfix returns the string representation of an expres-sion in postfix form. In the case of a LeafNode, that is the string representation of thenode's integer.class LeafNode(object):"""Represents an integer.def init (self, data):self. data data=def postfix (self):return str(self)def str (self):return str(self. data)An InteriorNode's postfix string contains the postfix strings of its two operand nodes,followed by the node's operator.class Interior Node (object):"""""Represents an operator and its two operands."def init (self, op, leftOper, rightOper):self. operator = opself. leftOperand=left0perself. rightOperand= rightOperdef postfix (self):"11"1Treesreturn self. leftoperand.postfix()+""+\self. rightOperand.postfix() + " " + \self. operatorChapter 10The design pattern of the postfix methods of Interior Node and Leaf Node is like the oneused for the traversals of binary trees. The only difference is that in this application, anexpression tree is never empty, so a leaf node is the base case. The other expression treetraversals have a similar design and are left as exercises for you.

Here is the implementation of the LeafNode and InteriorNode classes with the required methods: Code:…

Answered: Implement LeafNode and InteriorNode…

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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Question

Implement LeafNode and InteriorNode classes for the expression tree as discussed on this page

Use this template:

Please don't change any function names
Add any methods if necesssary
TODO: Remove the pass statements and implement the methods.
'''
class LeafNode:
def __init__(self, data):
self.data = data
def postfix(self):
return str(self)
def __str__(self):
return str(self.data)
def prefix(self):
pass
def infix(self):
pass
def value(self):
return self.data
class InteriorNode:
def __init__(self, op, left_op, right_op):
self.op = op
self.left_op = left_op
self.right_op = right_op
def postfix(self):
return self.left_op.postfix() + " " + self.right_op.postfix() + " " +
self.op
def prefix(self):
pass
def infix(self):
pass
def value(self):
pass
if __name__ == "__main__":
# TODO: (Optional) your test code here.
a = LeafNode(4)
b = InteriorNode('+', LeafNode(2), LeafNode(3))
c = InteriorNode('*', a, b)
c = InteriorNode('-', c, b)

316
The constructor for Leaf Node expects an integer as an argument, whereas the con-
structor for Interior Node expects a character-based operator symbol and two other
nodes as arguments.
Here is a short tester program that illustrates the use of the node classes:
from expressiontree import Leaf Node, InteriorNode
a = Leaf Node (4)
b
InteriorNode('+',
Leaf Node (2), Leaf Node (3))
c = InteriorNode('*',
a, b)
c = InteriorNode('-', c, b)
=
print("Expect ((4* (2+3)) - (2+3)):", c.infix())
print("Expect - *4 +23+23
:", c.prefix())
print("Expect 4 2 3+*23 + -
:", c.postfix())
print("Expect 15
:", c.value())
You now develop one of the traversal methods for both classes and leave the others as
exercises for you. The method postfix returns the string representation of an expres-
sion in postfix form. In the case of a LeafNode, that is the string representation of the
node's integer.
class LeafNode(object):
"""Represents an integer.
def init (self, data):
self. data data
=
def postfix (self):
return str(self)
def str (self):
return str(self. data)
An InteriorNode's postfix string contains the postfix strings of its two operand nodes,
followed by the node's operator.
class Interior Node (object):
"""
""Represents an operator and its two operands."
def init (self, op, leftOper, rightOper):
self. operator = op
self. leftOperand=left0per
self. rightOperand= rightOper
def postfix (self):
"11"1
Trees
return self. leftoperand.postfix()+""+\
self. rightOperand.postfix() + " " + \
self. operator
Chapter 10
The design pattern of the postfix methods of Interior Node and Leaf Node is like the one
used for the traversals of binary trees. The only difference is that in this application, an
expression tree is never empty, so a leaf node is the base case. The other expression tree
traversals have a similar design and are left as exercises for you.

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