How to Install Python 3.9 on the Raspberry Pi

What and why?

I use Python for various purposes all my Raspberry Pi boards. I run automated scripts, web applications that help in home automation, web controllable Christmas lights and more recently AI/machine learning.

The default Python that comes with Raspberry Pi OS is sometimes outdated, and I prefer to use the latest Python on python.org. You can manually install the latest version of Python using these steps.

Download Python 3.9 source

First, setup Raspberry Pi OS on your microSD card. You can read my previous blog post on how to do it.

Run this command to download the latest Python source code.

wget https://www.python.org/ftp/python/3.9.6/Python-3.9.6.tgz

Install the build tools

Run these to install the build tools.

sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev

If you want, you can install git as well.

sudo apt install git

Configure, make and make install

Run these commands. The configure command may take several minutes depending on your Raspberry Pi.

tar -xzvf Python-3.9.6.tgz 
cd Python-3.9.6/
./configure --enable-optimizations
sudo make altinstall

This will install Python at /usr/local/bin/python3.9. To test the version, run this:

/usr/local/bin/python3.9 -V

You will get this output:

Python 3.9.6

Make Python 3.9 the default version

When you run python, you will still get the default 3.7.3.

$ /usr/bin/python3 -V
Python 3.7.3

To make the default version of Python 3.9.6, run this:

sudo rm /usr/bin/python
sudo ln -s /usr/local/bin/python3.9 /usr/bin/python

Test whether Python 3.9.6 is the default version:

$ python -V
Python 3.9.6

Let me know whether you have any problems installing Python 3.9 in your Raspberry Pi.

Created on 10 August 2021