Setting up Your Python Environment (macOS)

Setting up a Python environment on your macOS computer is essential for development. This process is the first practical step towards writing and running your own Python programs.

macOS often includes an older version of Python pre-installed, primarily for compatibility with legacy system scripts. While convenient, this version might not be the one you want for active development. We strongly recommend installing the latest stable version directly from the official Python website to ensure you have access to the newest features, security updates, and consistent behavior across different projects.

Checking Your Current Python Version (Optional)

Before installing, you can check if Python 3 is already available on your system and which version it is.

1. Open the Terminal: You can find the Terminal application in your Applications folder, inside the Utilities subfolder. A quick way to open it is using Spotlight Search (Cmd + Spacebar) and typing "Terminal".
2. Check for Python 3: In the Terminal window, type the following command and press Enter:

   python3 --version
   

   If Python 3 is installed and configured correctly, you'll see output like Python 3.x.y (where x and y are version numbers). If you get a "command not found" error, or if the version shown is very old, proceed with the installation steps below.
3. Check for Python 2 (Legacy): You might also have Python 2. You can check this with:

   python --version
   

   You'll likely see Python 2.7.x. It's important not to use this version for modern Python development. Always use the python3 command (or just python after installing the official version, as we'll see).

Even if python3 --version shows a recent version, using the official installer ensures you have the standard setup expected by many tools and tutorials.

Downloading the Official Python Installer

1. Visit the Official Website: Open your web browser and navigate to the official Python website: https://www.python.org
2. Go to Downloads: Hover over the "Downloads" menu. It should automatically detect you are on macOS and suggest the latest stable version for download.
3. Download the Installer: Click the button labelled something like "Download Python 3.x.y". This will download a .pkg file (e.g., python-3.11.5-macos11.pkg). Download the latest stable release; avoid pre-releases or beta versions unless you have a specific reason.

Running the Installer

1. Open the .pkg File: Locate the downloaded .pkg file (usually in your Downloads folder) and double-click it to start the installation wizard.
2. Follow the Installation Steps:
   • You'll see an introduction screen. Click Continue.
   • Read the "Important Information" (Read Me) section. Click Continue.
   • Review the software license agreement. Click Continue, then Agree if you accept the terms.
   • On the "Installation Type" screen, you can usually just click Install. It will show the required disk space and install location (typically /Library/Frameworks/Python.framework). You generally don't need to customize the location.
   • You might be prompted to enter your administrator password to authorize the installation. Enter it and click Install Software.
   • The installer will copy the necessary files. Once it's finished, you should see a confirmation screen indicating the installation was successful. It often includes information about the installed components, including IDLE (a simple integrated development environment) and notes about the PATH. Click Close. You can move the installer file to the Trash if prompted.

The installer typically configures your system so that the python3 command points to the newly installed version.

Verifying the Installation

It's important to confirm that the installation worked and that your system recognizes the new Python version.

1. Open a New Terminal Window: Close any existing Terminal windows and open a fresh one. This ensures that any changes made to your system's configuration (like updating the PATH) are loaded correctly.
2. Check the Python 3 Version: Type the following command and press Enter:

   python3 --version
   

   You should now see the specific version number you just installed (e.g., Python 3.11.5). If you still see an old version or get an error, double-check the installation steps or consult the Python documentation for troubleshooting.
3. Check the pip Version: pip is the package installer for Python, used to add libraries and tools. It's included with the official Python installer. Verify it by running:

   pip3 --version
   

   This should output the version of pip bundled with your Python installation and its location. We'll use pip later in the course to install external packages.

Using the Python Interpreter (REPL)

With Python installed, you can now interact with it directly using its Read-Eval-Print Loop (REPL). This is a great way to experiment with simple code snippets.

1. Start the REPL: In your Terminal window, simply type python3 and press Enter.

   python3
   

2. See the Prompt: You'll see some information about the Python version and then the interpreter prompt: >>>. This means Python is waiting for you to type commands.
3. Run a Command: Type a simple Python command, like printing a message, and press Enter:

   >>> print("Hello from Python on macOS!")
   

   Python will execute the command immediately and display the output:

   Hello from Python on macOS!
   >>>
   

   The >>> prompt reappears, ready for your next command.
4. Exit the REPL: To leave the interactive interpreter and return to your regular Terminal prompt, you can type exit() and press Enter, or press Ctrl+D.

   >>> exit()
   

Congratulations! You have successfully installed Python on your macOS system, verified the installation, and interacted with the Python REPL. You now have a working environment ready for writing and running your first Python scripts, which we will cover shortly.