Adapter Pattern

Objectives

During this activity:

Students will write and test Python code that implements the Adapter pattern.

This activity helps students develop the following skills, values and attitudes: ability to analyze and synthesize, capacity for identifying and solving problems, and efficient use of computer systems.

Activity Description

This activity must be developed individually.

Create a directory called adapter containing three files: simple_queue.py, queue_to_stack_adapter.py, and adapter_test.py.

Add to the queue_to_stack_adapter.py Python source file a comment at the start containing title, date, and the author’s personal information. For example:
```
# Adapter Pattern
# Date: 23-May-2022
# Authors:
#          A01777771 Stephen Strange
```

The content of the file simple_queue.py is as follows:

# File: simple_queue.py

# IMPORTANT: Do not modify the following class in any way!

class SimpleQueue:

    def __init__(self):
        self._info = []

    def insert(self, x):
        self._info.append(x)
        return self

    def remove(self):
        if self.is_empty():
            raise RuntimeError("Can't remove if queue is empty")
        else:
            return self._info.pop(0)

    def is_empty(self):
        return self.size() == 0

    def size(self):
        return len(self._info)

    def __repr__(self):
        return repr(self._info)

The SimpleQueue class contains a First-In First-Out (FIFO) data structure that implements the following methods:

Method Signature	Description
`insert(self, x)`	Inserts x at the back of this queue. Returns this queue.
`remove(self)`	Removes and returns the element at the front of this queue. Raises an exception if this queue happens to be empty.
`is_empty(self)`	Returns `True` if this queue is empty, otherwise returns `False`.
`size(self)`	Returns the number of elements currently stored in this queue.

Write an adapter class called QueueToStackAdapter (place it in the file called queue_to_stack_adapter.py) that makes a SimpleQueue instance (as implemented above) behave like a Last-In First-Out (LIFO) stack with the following interface:

Method Signature	Description
`__init__(self, queue)`	Initializes a new stack, using queue as the adaptee.
`push(self, x)`	Inserts x at the top of this stack. Returns this stack.
`pop(self)`	Returns `None` if this stack is empty, otherwise removes and returns its top element.
`peek(self)`	Returns `None` if this stack is empty, otherwise returns its top element without removing it.
`is_empty(self)`	Returns `True` if this stack is empty, otherwise returns `False`.
`size(self)`	Returns the number of elements currently stored in this stack.

The following unit test verifies the correct behavior of the QueueToStackAdapter class. Place the test class in the adapter_test.py source file.

# File: adapter_test.py

from unittest import TestCase, main
from simple_queue import SimpleQueue
from queue_to_stack_adapter import QueueToStackAdapter


class TestQueueToStackAdapter(TestCase):

    def test_queue_to_stack_adapter(self):
        q = SimpleQueue()
        qsa = QueueToStackAdapter(q)
        self.assertTrue(q.is_empty())
        self.assertTrue(qsa.is_empty())
        self.assertIsNone(qsa.pop())
        self.assertIs(qsa, qsa.push('Foo'))
        self.assertEqual('Foo', qsa.peek())
        self.assertFalse(q.is_empty())
        self.assertFalse(qsa.is_empty())
        self.assertIs(qsa, qsa.push('Bar'))
        self.assertEqual('Bar', qsa.peek())
        self.assertEqual(qsa, qsa.push('Baz').push('Quux'))
        self.assertEqual(4, q.size())
        self.assertEqual(4, qsa.size())
        self.assertEqual('Quux', qsa.peek())
        self.assertEqual('Quux', qsa.pop())
        self.assertEqual('Baz', qsa.peek())
        self.assertEqual('Baz', qsa.pop())
        self.assertEqual('Bar', qsa.peek())
        self.assertEqual('Bar', qsa.pop())
        self.assertEqual('Foo', qsa.peek())
        self.assertIs(qsa, qsa.push('Goo'))
        self.assertEqual('Goo', qsa.peek())
        self.assertEqual('Goo', qsa.pop())
        self.assertEqual('Foo', qsa.peek())
        self.assertEqual(1, qsa.size())
        self.assertEqual('Foo', qsa.pop())
        self.assertIsNone(qsa.peek())
        self.assertIsNone(qsa.pop())
        self.assertTrue(q.is_empty())
        self.assertTrue(qsa.is_empty())
        self.assertEqual(0, q.size())
        self.assertEqual(0, qsa.size())


if __name__ == '__main__':
    main()

To run the tests, at the terminal move to the adapter directory:

cd adapter

Now, run the script with the tests and make sure you pass them all:

python3 adapter_test.py

Deliverables

Instrucciones para subir archivo

Para entregar el archivo queue_to_stack_adapter.py, ingresa los siguientes datos:

Solicitar NIP

Due date is Tuesday, May 24.