IT$209-$ LAB ASSIGNMENT $6($LA$6)$

ENHANCED Cart Class $-\text{'}$in$\text{'}$ Operator, 'list' Subclass

This Lab has two parts. In Part $1$ you are to modify the Cart class created in a previous lab so that it

works with the built$-$in Python $\text{'}$in$\text{'}$ operator. The result will be that code using the Cart class can check

to see whether an item is already in the cart using $\text{'}$in$\text{'}.$ Part $2$ requires you to modify the Cart class to

be a subclass of 'list'. You may use your previously created Cart class or the one l$\text{'}$m providing with

this assignment.

Part $1$

Recall that adding a $\text{'}\text{'}$ method to a class causes Python to treat that class as a "duck

type" subclass of the built$-$in Container abstract base class. As a result the Python interpreter

recognizes when the $\text{'}$in$\text{'}$ operator is used with the class and substitutes the logic of the provided

$\text{'}\text{'}$ method if one is provided. If not provided, Python raises an exception. Test code is

provided with this assignment that will create a Cart object, several Item objects, and then run tests

using $\text{'}$in$\text{'}.$

To complete this part, create a Cart method to check whether an item is contained in the Cart object

when code using the Cart class uses $\text{'}$in$\text{'}.$ When you inspect the test code you'll notice that $\text{'}$in$\text{'}$ can be

invoked with either an Item object $($i$.$e$.\text{'}$i$1\text{'},$ type "Item"$)$ or just the name of the item $($i$.$e$.$ 'eggs', type

string$).$ Your method must detect which type is submitted and perform the test accordingly.

Part $2$

Modify the Cart class $-$ either your own or the one I provide $-$ to be a subclass of list. In doing this

you'll be extending the built$-$in list class. Everything true about a Python list will also be true about

Cart, except you've added additional logic specific to Cart objects $($e$.$g$.,$ customer name, cart

sequence number$).$

The major difference is that instead of having an internal list, self.contents, to hold the items in the

cart, the Cart object itself is a list. You refer to the items in Cart method code by just using 'self. For

example, when adding item 'itemObj' you issue the statement 'self.append$($itemObj$)\text{'}.$ Likewise,

self$[0]$ refers to the first item in the list, self$[1]$ the second, etc. To complete this part modify the Cart

class to do just that. If you do this correctly the test code provided with the assignment will work with

both Part $1$ and $2$ without modification.

Provided Code and Test Script

A $\text{'}.$py$\text{'}$ template file is provided with this assignment that contains code for the Cart and item classes,

as well as a test script. Modify this Cart class, or use your own, for both parts using the template file

as a starting point for both. Copy the template into your own file and complete Part $1.$ Then copy it

again into another file and complete Part $2.$ The test script can be used for both parts and should run

without modification. As was mentioned before, please be aware that the script is not an exhaustive

test, so please perform some testing beyond what's in the script. It's an unfortunate reality of

software development that testing can only expose errors and not prove the lack of errors. Even the

most exhaustive testing cannot guarantee defect$-$free software.

This lab should require creating around $10$ lines of new code for Part $1$ and modifying around $7$ lines

for Part $2.$

What and where to submit:

Submit by uploading two files, one for each part, with the Python code to Blackboard

Submit the programs using the file template provided with the Lab assignment specification

Input a short set of comments as the first lines that identify the program, its purpose, and its

author. Also include other comments where you think necessary.

Include a screen shot of the program's output using, at minimum, the display output resulting from

running the test script

How the assignment will be assessed:

The Python code will be visually inspected and executed via command line $("$python