Installing Python

Keywords: python

Windows

Click the following image to be redirected to a 2-minute YouTube walkthrough.

1. First, open the url https://www.python.org/downloads/ in any web browser.

2. As of June 2021, the latest version of Python is 3.9.6. You may see a different number. We recommend you use the newest official version which is provided to you by simply clicking the button under “Download the latest version for Windows”.

3. Once the download has completed, open the file by clicking on it in your Downloads pane.

4. Be sure to check the box that reads “Add Python x.x to PATH”. This will allow you to run commands from the terminal/command prompt.

5. Click “Install Now”. The default options that entail this selection are appropriate.

   1. The UAC prompt will pop up. UAC stands for “User Account Control” and exists so that the computer will not have unauthorized changes performed on it. Click “Yes” because Python is safe. School-issued computers may ask for an administrator password, so contact your IT department or professor.

6. The installation will take some time.

7. If the setup was successful, then it will say so. Click “Close”.

8. Click the “Type here to search” box in the bottom-left of the screen, type “cmd”, and press Enter.

   1. An alternative method is to press the Windows key and the “R” key at the same time, type “cmd”, and press Enter. This is convenient for those who like to use the keyboard.

9. Type python --version and the output should read “Python x.x.x”; as long as it is the latest version from the website, congratulations. Python is installed on the computer.

Mac

Click the following image to be redirected to a 5-minute YouTube walkthrough. (Yes, Mac’s video is a little longer, but do not fret! You can skip to the 1:00 minute mark if you are in a hurry.)

1. First, open the url https://www.python.org/downloads/ in any web browser.

2. Underneath Download the latest version for Mac OS X, there should be a yellow button that reads Download Python x.x.x. Click on it, and the download should commence.

3. Once the download finishes, open it by clicking on it. The installer will open. Click Continue, click Continue again, and click Continue again. Read the agreements.

4. Click Agree.

   1. If you want to check how much free storage you have on your computer, click the Apple icon in the top left of your computer. Click About This Mac and then click on Storage. As of July 2021, Python takes ~120 MB of space. Remember that 1 GB = 1000 MB.

5. Click Install. Enter your password and press Enter. The installation will take a while.

6. A Finder window will open. You can close it as it is unnecessary. Click Close in the bottom-right of the installer. Click Move to Trash because you do not need the installer anymore.

7. Next confirm that Python installed correctly. Click the magnifying glass in the top-right of your screen and then type terminal into Spotlight Search. Double-click Terminal.

   1. The terminal will be used frequently. Consider keeping it in the dock for convenience. Click and hold the Terminal in the dock, go to Options, and click Keep in Dock.

8. Type python3 --version into the terminal and press Enter. It should output the latest version of Python. Congratulations!

Linux

Click the following image to be redirected to a 9-minute YouTube walkthrough. (Linux’s tutorial is the longest, but it is worth it.) This tutorial uses Ubuntu, but it should work on other Linux distros, as well.

• Naturally we recommend that you read all of the licensing information.

1. First, open the url https://www.python.org/downloads/ in any web browser.

2. Look at the latest version. It is on the yellow button: Download Python x.x.x. You do not need to click this button. Remember this version number.

3. Open a terminal by pressing the Windows key or by clicking the grid on the bottom left of your screen. Type terminal. Click on the Terminal result that appears.

4. Next, prepare your system:

Note: If you want to check how much disk space you have, you can use

$ df -h /
Filesystem       Size   Used  Avail Capacity iused       ifree %iused  Mounted on
/dev/disk1s5s1  1.8Ti   14Gi  387Gi     4%  553757 19538475003    0%   /

The value under Avail will be your available space. Make sure you have sufficient space.

$ sudo apt-get update
$ sudo apt install -y wget curl
$ sudo apt install -y openssl libssl-dev
$ sudo apt install -y build-essential zlib1g-dev libncurses5-dev 
$ sudo apt install -y libgdbm-dev libnss3-dev  libreadline-dev libffi-dev libsqlite3-dev libbz2-dev

5. After this finishes, type cd /opt and press Enter. Then, remember which version you read on the Python webpage (the latest version) and add it as environment variable PV to your terminal so we can more easily execute commands that include the version number. Type:

   $ PV=3.9.6
   $ sudo wget https://www.python.org/ftp/python/$PV/Python-$PV.tgz
   $ sudo tar xzvf Python-$PV.tgz
   $ cd Python-$PV
   $ ./configure --enable-optimizations
   $ make
   $ sudo make altinstall
   

6. Confirm Python’s successful installation by typing pythonx.x --version; be sure to replace x.x with the first two numbers of the version number. It should output the latest version number. Congratulations!

Python venv

Before you install packages, you need to create a Python venv in your local environment. We typically do this with

$ python3.9 -m venv ~/ENV3
$ source ~/ENV3/bin/activate

or for Windows executed in git bash

$ python -m venv ~/ENV3
$ source ~/ENV3/Scripts/activate

Troubleshooting

Incorrect Python Version on Command Prompt (Windows)

If the Windows computer has previously installed an older version of Python, running python --version on Command Prompt may output the previously installed older version. Typing python3 --version may output the correct, latest version.