Resources Online

Resources Online#

This book is designed for the introductory computer science course at Loyola University Chicago. The materials are available to all on the web.

Note

For all work in this course, install Python 3 and use the command-line tools. The basic workflow is:

  1. Write a .py file in a text editor (Vim or Emacs recommended).

  2. Run it from the terminal:

    python3 filename.py

You can also experiment interactively by typing python3 at the terminal to enter the interactive shell.

  • The course example repository will contain all example programs referenced in the book. Download or clone it and keep it alongside your work.

  • python.org is the official Python website. It includes documentation for the standard library and language reference.

  • We recommend learning a terminal-based editor such as Vim or GNU Emacs. Mastering one of these builds habits — editing, navigating, and running code — that transfer directly to any command-line environment. Visual Studio Code is an acceptable alternative, but you will get more out of it once you are comfortable working between an editor and the shell.

The Interactive Shell#

Python provides an interactive shell (also called a REPL, for Read-Evaluate-Print Loop) that lets you type expressions and see their values immediately. Start it by typing python3 at your terminal:

$ python3
Python 3.12.0 (default, ...)
Type "help", "copyright", "credits" or "license" for more information.
>>>

Type any expression and press Enter:

>>> 2 + 3
5
>>> "Hello, world!"
'Hello, world!'

This is very useful for experimenting with small pieces of code. We will use the >>> prompt throughout the book to show interactive examples.

To exit the shell, type quit() or press Ctrl-D.

Running Code in Your Browser#

Many examples in this book sit behind a Try it live ▶ button. Click it and the example turns into a live, editable Python cell that runs right on the page — no installation, no account, and nothing sent to a server. This is powered by JupyterLite and Pyodide (a build of Python that runs inside your web browser). Edit the code, run it again, and experiment freely; your changes are not saved, so reload the page to start over. The first run takes a few seconds while Python loads.

Here is a tiny example to try right now. Click Try it live, run it, then change the greeting and run it again — the date and time will be the moment you run it:

>>> print("Hello, world!")
Hello, world!
>>> from datetime import datetime
>>> print("The current date and time is", datetime.now())
The current date and time is 2026-06-18 09:15:42.531809

The time shown above is only a sample; running the cell prints your computer’s current date and time. This in-browser execution has limits — examples that read files or use the network cannot run there — so for coursework you will still use a local Python installation, as described above.

Alternate Formats#

This book is available in HTML, PDF, and EPUB formats. See the download links at the top of each page.