Python3

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This is exp_eval_tests

# Start of unittest - add to completely test functions in exp_eval

import unittest

from exp_eval import *

class test_expressions(unittest.TestCase):

def test_postfix_eval_01(self):

self.assertAlmostEqual(postfix_eval("3 5 +"), 8)

def test_postfix_eval_02(self):

try:

postfix_eval("blah")

self.fail()

except PostfixFormatException as e:

self.assertEqual(str(e), "Invalid token")

def test_postfix_eval_03(self):

try:

postfix_eval("4 +")

self.fail()

except PostfixFormatException as e:

self.assertEqual(str(e), "Insufficient operands")

def test_postfix_eval_04(self):

try:

postfix_eval("1 2 3 +")

self.fail()

except PostfixFormatException as e:

self.assertEqual(str(e), "Too many operands")

def test_infix_to_postfix_01(self):

self.assertEqual(infix_to_postfix("6 - 3"), "6 3 -")

self.assertEqual(infix_to_postfix("6"), "6")

def test_prefix_to_postfix(self):

self.assertEqual(prefix_to_postfix("* - 3 / 2 1 - / 4 5 6"), "3 2 1 / - 4 5 / 6 - *")

if __name__ == "__main__":

unittest.main()

This is exp_eval

from stack_array import Stack

# You do not need to change this class

class PostfixFormatException(Exception):

pass

def postfix_eval(input_str):

"""Evaluates a postfix expression"""

"""Input argument: a string containing a postfix expression where tokens

are space separated. Tokens are either operators + - * / ^ or numbers

Returns the result of the expression evaluation.

Raises an PostfixFormatException if the input is not well-formed"""

pass

def infix_to_postfix(input_str):

"""Converts an infix expression to an equivalent postfix expression"""

"""Input argument: a string containing an infix expression where tokens are

space separated. Tokens are either operators + - * / ^ parentheses ( ) or numbers

Returns a String containing a postfix expression """

pass

def prefix_to_postfix(input_str):

"""Converts a prefix expression to an equivalent postfix expression"""

"""Input argument: a string containing a prefix expression where tokens are

space separated. Tokens are either operators + - * / ^ parentheses ( ) or numbers

Returns a String containing a postfix expression(tokens are space separated)"""

pass