Installing Python

Purpose

This document describes how to install Python on your personal machine.

Prerequisites

You’ll need administrative access to your machine.

Is Python already installed?

Check to see if you have Python installed already.

Mac OS

Open a terminal and try these commands:

python --version

If you have Python 3.7.6 or greater, then you’re already set. Ignore the rest of this how-to.

Windows

Open the Command Prompt or Windows PowerShell application. You can access these by entering command or powershell in the search window in the Windows 10 toolbar. Enter this command at the prompt:

python --version

If the command returns Python 3.7.6 or a later version, you’re set.

Installing Python

Which Python version?

You want to use Python 3. The latest version as of 2020-03-17 is 3.8.2, but I recommend using the most recent stable version (3.7.7). Python 2 is no longer under active development. There is a still-smouldering flame war between the Python 2 and Python 3 communities. Remember my adage–avoid flame wars. Go with Python 3.

Mac OS X

Homebrew on Mac OS X

If you own your own machine, I strongly recommend using the Homebrew package manager.

Uninstall old version of Homebrew

If you’ve installed Homebrew some time ago, you may want to uninstall it before reinstalling.

Enter the following command in a terminal:

ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"

Install new version of Homebrew

Follow the instructions here to install Homebrew:

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

Install Python3 under Homebrew

Enter the following command in a terminal to install Python3:

brew install python3

Alternatives to Homebrew

It’s fine if you want to install Python 3 directly from the Python site or use Anaconda or another tool. My main beef with the Conda package manager is that it seems to support fewer Python packages than the alternatives.

Windows

I had good luck installing Python following the instructions on https://www.python.org/downloads/windows/. Again, I suggest you download the latest stable release (3.7.7 as of 2020-03-17).

This will download an installer program. Launch it and follow the steps.

You may also want to consider Anaconda.

Test your Python3 installation

From a Mac OS terminal or the Windows Command Prompt or Windows PowerShell application enter the following command:

python --version

With luck, this should return Python 3.7.7 or something similar.

Optional Python3 test drive

To open a Python session, enter python at the Mac OS terminal or the Windows Command Prompt or Windows PowerShell prompt. This will open an interactive Python session that should look something like this:

Python 3.7.6 (default, Mar  6 2020, 14:33:20)
[Clang 11.0.0 (clang-1100.0.33.17)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>

You can start entering Python commands or type exit() and press return to exit.

Download packages

If you’ve used Homebrew to install Python on Mac OS or the Python.org installer on Windows, you can use the pip package manager to install packages. These commands work in the Mac OS terminal or the Windows Command Prompt or Windows PowerShell application.

Note: I suggest using the explicit pip3 command in case you have multiple versions of Python installed. For example, Mac OS comes with Python 2.7. I do not think that Windows comes with a Python installation, so if you install Python 3 and Python 3 alone, you should be able to use python to launch Python 3 pip to run pip3.

pip3 install jupyter
pip3 install pandas
pip3 install numpy
pip3 install matplotlib

In some cases, you may get an error with these commands because they install the packages globally–for all users. If so, then add the --user flag:

pip3 install --user jupyter
pip3 install --user pandas
pip3 install --user numpy
pip3 install --user matplotlib