Behind the scenes, today’s websites are actually rich applications that act like fully developed desktop applications. Python has a great set of tools for building web applications. In this chapter you’ll learn how to use Django (http://djangoproject.com/) to build a project called Learning Log—an online journal system that lets you keep track of information you’ve learned about particular topics.
TRY IT YOURSELF #1
18-1. New Projects: To get a better idea
of what Django does, build a couple of empty projects and look at what
it creates. Make a new folder with a simple name, like InstaBook or
FaceGram (outside of your learning_log directory), navigate to that
folder in a terminal, and create a virtual environment. Install Django,
and run the command django-admin.py startproject instabook. (make sure
you include the dot at the end of the command).
Look at the files and folders this command creates, and compare them to Learning Log. Do this a few times until you’re familiar with what Django creates when starting a new project. Then delete the project directories if you wish.
TRY IT YOURSELF #2
18-2. Short Entries: The __str__()
method in the Entry model currently appends an ellipsis to every
instance of Entry when Django shows it in the admin site or the shell.
Add an if statement to the __str__() method that adds an ellipsis
only if the entry is more than 50 characters long. Use the admin site to
add an entry that’s fewer than 50 characters in length, and check that
it doesn’t have an ellipsis when viewed.
18-3. The Django API: When you write code to access the data in your project, you’re writing a query. Skim through the documentation for querying your data at https://docs.djangoproject.com/en/3.2/topics/db/queries/. Much of what you see will look new to you, but it will be quite useful as you start to work on your own projects.
18-4. Pizzeria: Start a new project
called pizzeria with an app called pizzas. Define a model Pizza
with a field called name, which will hold name values such as
Hawaiian and Meat Lovers. Define a model called Topping with
fields called pizza and name. The pizza field should be a foreign
key to Pizza, and name should be able to hold values such as
pineapple, Canadian bacon, and sausage.
Register both models with the admin site, and use the site to enter some pizza names and toppings. Use the shell to explore the data you entered.
TRY IT YOURSELF #3
18-5. Meal Planner: Consider an app that
helps people plan their meals throughout the week. Make a new folder
called meal_planner, and start a new Django project inside this
folder. Then make a new app called meal_plans. Make a simple home page
for this project.
18-6. Pizzeria Home Page: Add a home page to the Pizzeria project you started in Exercise 18-4 (page 412).
TRY IT YOURSELF #4
18-7. Template Documentation: Skim the Django template documentation at https://docs.djangoproject.com/en/3.2/ref/templates/. You can refer back to it when you’re working on your own projects.
18-8. Pizzeria Pages: Add a page to the Pizzeria project from Exercise 18-6 (page 416) that shows the names of available pizzas. Then link each pizza name to a page displaying the pizza’s toppings. Make sure you use template inheritance to build your pages efficiently.