Installation instructions on a Mac

Installing Python 3

The Python installation also includes IDLE, the program we will use to write and execute our Python programs.

1. Go to the download page for Python 3.
2. Download the latest version of Python 3 by clicking the appropriate Download button. (At the time these instructions were created, the latest version of Python 3 was Python 3.6.0. If you see a later version number, that’s okay, too. Just make sure to select the button for the version number that begins with Python 3 and not Python 2.)
3. Double-click on the downloaded file in your Downloads folder (the name of the file should begin with python and end with .pkg). This should start an automatic installer.
4. You should be able to use all of the default settings that the installer gives you. Wait for the installer to finish and then close it. You can now delete the installer by dragging the .pkg file to the Trash.
5. In your Applications folder, you should now be able to find a Python 3 folder. Under that folder, the IDLE application should be present.

The newest version of Python is “signed” as a safe application, so OS X should not have a problem installing it. If OS X prevents you from installing Python because it does not pass a security check, you should be sure you are downloading the most recent Python version.

Installing the Java runtime environment

The Java runtime environment is also known as the JRE.

1. Go to the download page for Java 8.
2. Find the first table of download links (the one for Java SE Runtime Environment 8u161).
3. Accept the Oracle Binary Code License Agreement by selecting the Accept License Agreement radio button.
4. Click the download link for Mac OS X x64 — use the file that ends with .dmg.
5. If you receive an error message that says you are downloading from an unsafe or unknown site, you’ll need to change your security preferences, at least temporarily, by taking the steps outlined in the Lowering your security settings section below.
6. Click the .dmg file to mount the Java installation disk image.
7. If the mounted image doesn’t show up in a Finder window, open a new Finder window and select the disk image from the sidebar. Once open, double-click on the .mpkg file to start the installer.
8. You should be able to use all of the default settings that the installer gives you. Wait for the installer to finish and then close it. You can now unmount the disk image by clicking the eject icon in the sidebar or dragging it to the Trash. Then you can delete the .dmg file by dragging it to the Trash.

Lowering security settings

OS X may stop you from downloading or running applications downloaded from the Web (as opposed to through the Mac App Store) unless you lower your security settings. Here’s how to adjust them so that you may install and run applications from anywhere:

1. Open System Preferences, located under the Apple menu in the top left corner.
2. In the Security & Privacy preference pane, click the lock icon and authenticate as an administrator user.
3. Make sure the radio button under Allow applications downloaded from: is set to Anywhere.
4. Re-download or re-open the desired application.