# 0.3: Using the code


All code used in this book is available from a Git repository on GitHub: http://thinkcomplex.com/repo. If you are not familiar with Git, it is a version control system that allows you to keep track of the files that make up a project. A collection of files under Git’s control is called a “repository”. GitHub is a hosting service that provides storage for Git repositories and a convenient web interface.

The GitHub homepage for my repository provides several ways to work with the code:

• You can create a copy of my repository by pressing the Fork button in the upper right. If you don’t already have a GitHub account, you’ll need to create one. After forking, you’ll have your own repository on GitHub that you can use to keep track of code you write while working on this book. Then you can clone the repo, which means that you copy the files to your computer.
• Or you can clone my repository without forking; that is, you can make a copy of my repo on your computer. You don’t need a GitHub account to do this, but you won’t be able to write your changes back to GitHub.
• If you don’t want to use Git at all, you can download the files in a Zip file using the green button that says “Clone or download”.

I developed this book using Anaconda from Continuum Analytics, which is a free Python distribution that includes all the packages you’ll need to run the code (and lots more). I found Anaconda easy to install. By default it does a user-level installation, not system-level, so you don’t need administrative privileges. And it supports both Python 2 and Python 3. You can download Anaconda from continuum.io/downloads.

The repository includes both Python scripts and Jupyter notebooks. If you have not used Jupyter before, you can read about it at https://jupyter.org.

There are three ways you can work with the Jupyter notebooks:

Run Jupyter on your computer

If you installed Anaconda, you can install Jupyter by running the following command in a terminal or Command Window:

$conda install jupyter Before you launch Jupyter, you should cd into the directory that contains the code:$ cd ThinkComplexity2/code

And then start the Jupyter server:

\$ jupyter notebook

When you start the server, it should launch your default web browser or create a new tab in an open browser window. Then you can open and run the notebooks.

Run Jupyter on Binder

Binder is a service that runs Jupyter in a virtual machine. If you follow this link, thinkcomplex.com/binder, you should get a Jupyter home page with the notebooks for this book and the supporting data and scripts.

You can run the scripts and modify them to run your own code, but the virtual machine you run them in is temporary. If you leave it idle, the virtual machine disappears along with any changes you made.

View notebooks on GitHub

GitHub provides a view of the notebooks you can can use to read the notebooks and see the results I generated, but you won’t be able to modify or run the code.

Good luck, and have fun!

Allen B. Downey
Professor of Computer Science
Olin College of Engineering
Needham, MA

## Contributor List

If you have a suggestion or correction, please send email to downey@allendowney.com. If I make a change based on your feedback, I will add you to the contributor list (unless you ask to be omitted).

Let me know what version of the book you are working with, and what format. If you include at least part of the sentence the error appears in, that makes it easy for me to search. Page and section numbers are fine, too, but not quite as easy to work with. Thanks!

• John Harley, Jeff Stanton, Colden Rouleau and Keerthik Omanakuttan are Computational Modeling students who pointed out typos.
• Jose Oscar Mur-Miranda found several typos.
• Phillip Loh, Corey Dolphin, Noam Rubin and Julian Ceipek found typos and made helpful suggestions.
• Sebastian Schöner sent two pages of corrections!
• Philipp Marek sent a number of corrections.
• Jason Woodard co-taught Complexity Science with me at Olin College, introduced me to NK models, and made many helpful suggestions and corrections.
• Davi Post sent several corrections and suggestions.
• Graham Taylor sent a pull request on GitHub that fixed many typos.

I would especially like to thank the technical reviewers, Vincent Knight and Eric Ma, who made many helpful suggestions, and the copy editor, Charles Roumeliotis, who caught many errors and inconsistencies.

Other people who reported errors include Richard Hollands, Muhammad Najmi bin Ahmad Zabidi, Alex Hantman, and Jonathan Harford.