Due Monday Mar 6 at 9pm. Upload to Desire 2 Learn dropbox for homework 7.
You are going download the array_stack_hw7.py source code file. It contains a definition of a stack ADT implemented as an array. This file also contains a set of unit tests that test each method of the ArrayStack class. Your task is the following:
A. Implement the following ArrayStack methods (please note the comments indicating HOW these should be implemented):
get_data(self)push_seq(self, seq)as_string(self)B. Implement all of the test methods in TestLinkedStackMethods:
C. Run your file to run the unit tests. All tests should pass for full credit. Recursion REQUIRED where noted.
DSAP Chapter 6 & 7
Your submission your source code file named according to syllabus.
# hw 7 solution
import unittest
class EmptyStack(Exception):
"""Custom Exception"""
def __init__(self, value):
self.value = value
def __str__(self):
return repr(self.value)
class ArrayStack:
"""LIFO Stack implementation using a Python list as underlying storage."""
def __init__(self):
"""Create an empty stack."""
self._data = [] # nonpublic list instance
def __len__(self):
"""Return the number of elements in the stack."""
return len(self._data)
def is_empty(self):
"""Return True if the stack is empty."""
return len(self._data) == 0
def push(self, e):
"""Add element e to the top of the stack."""
self._data.append(e) # new item stored at end of list
def top(self):
"""Return (but do not remove) the element at the top of the stack.
Raise Empty exception if the stack is empty.
"""
if self.is_empty():
raise EmptyStack('Stack is empty')
return self._data[-1] # the last item in the list
def pop(self):
"""Remove and return the element from the top of the stack (i.e., LIFO).
Raise Empty exception if the stack is empty.
"""
if self.is_empty():
raise EmptyStack('Stack is empty')
return self._data.pop() # remove last item from list
def get_data(self):
"""returns the underlying data structure for the stack."""
return self._data
def push_seq(self, seq):
"""Iteratively push each element in seq to stack."""
for i in seq:
self.push(i)
def as_string(self, s):
"""Recursively build a string containing each element of the stack without modifying the stack.
The final string should contain each element of the stack separated by a space. This time though
the BOTTOM of the stack should be first and the TOP of the stack should be last.
"""
if not s:
return ''
return (self.as_string(s[1:]) + ' ' + str(s[0])).strip() # make sure to strip leading and trailing whitespace.
class TestArrayStackMethods(unittest.TestCase):
"""Unit tests for ArrayStack"""
def test_init(self):
stack = ArrayStack()
self.assertEqual(len(stack), 0)
def test_is_empty(self):
stack = ArrayStack()
self.assertEqual(stack.is_empty(), True)
def test_push(self):
stack = ArrayStack()
stack.push(5)
self.assertEqual(stack.top(), 5)
def test_push_seq(self):
stack = ArrayStack()
stack.push(0)
stack.push_seq([1, 3, 5, 7, 9])
self.assertEqual(stack.top(), 9)
self.assertEqual(len(stack), 6)
def test_top(self):
stack = ArrayStack()
stack.push(5)
self.assertEqual(stack.top(), 5)
def test_top_exception(self):
"""Tests whether top correctly raises EmptyStack exception."""
stack = ArrayStack()
with self.assertRaises(EmptyStack):
stack.top()
def test_pop(self):
stack = ArrayStack()
stack.push(5)
self.assertEqual(stack.pop(), 5)
def test_get_data(self):
stack = ArrayStack()
stack.push_seq([1, 3, 5, 7, 9])
self.assertEqual(stack.get_data(), [1, 3, 5, 7, 9])
def test_pop_exception(self):
"""Tests whether pop correctly raises EmptyStack exception."""
stack = ArrayStack()
with self.assertRaises(EmptyStack):
stack.pop()
def test_as_string(self):
"""Tests that as_string correctly lists the contents of the stack in indicated order (bottom -> top)."""
stack = ArrayStack()
stack.push_seq([1, 3, 5, 7, 9])
self.assertEqual(stack.as_string(stack.get_data()), '9 7 5 3 1')
"""Run the unit tests on invocation of this file with python interpreter.
> python <name of this file>.py
"""
if __name__ == '__main__':
unittest.main()