Python Projects for Beginners a ten-Week Bootcamp Approach to Python Programming

Friday: Creating a Shopping Cart
For today’s project, we’re going to build an application that stores products within a list. We’ll be able to add, remove, clear, and show the products in the cart. All the concepts taught throughout the past few weeks will be used.
To follow along with this lesson, let’s continue from our previous notebook file
“Week_05” and add a markdown cell at the bottom that says, “Friday Project: Creating a Shopping Cart.”
CHapTeR 5 FUnCTIonS

Final Design

As we’ve introduced functions this week, the final design will be based around the logic of our program’s actions. Functions perform a specific task, which is usually an action. For our shopping cart program, the actions that we need to consider are the tasks of adding, removing, clearing, and showing the items within the cart. The logical design will look like Figure 5-5.

Figure 5-5. Shopping cart program logic
We’ll be sure to have one main function that will contain the loop and handle user input.

Initial Setup

Like the project from last week, we’ll be creating the program in a single cell, so make sure you familiarize yourself with the concepts we used in that project. To start, let’s import the clearing function from Jupyter Notebook and declare a global variable to work with:

1| # import necessary functions
2| from IPython.display import clear_output
4| # global list variable
5| cart = [ ]

We wanted to declare a global variable of cart to work with throughout this program. We’re going to use a list, as we’ll need to store several items. Using a list will also allow us to edit the variable directly without having to pass it around because of how item assignments work.

Adding Items

As stated in the initial design, we’ll want to create our functions first. We’ll start with the function for adding items to our cart variable:

7| # create function to add items to cart 8| def addItem(item):
9| clear_output( )
10| cart.append(item)
11| print( "{ } has been added.".format(item) )

We won’t call this function until later when we create the main loop. When called, this function will clear the output, append the item passed into the parameter, and output to the user.