How to Install Python 3.9 on Linux Mint 20

Python is one of the most popular programming languages used today for software development, data analysis, machine learning, and more. The latest major version, Python 3.9, was released on October 5, 2020 and includes many new features and optimizations.

In this comprehensive guide, we will cover how to install Python 3.9 on Linux Mint 20 via two methods:

1. Using the Deadsnakes PPA repository (recommended)
2. Building from source code

We will also demonstrate how to verify the installation and troubleshoot any issues.

Prerequisites

Before installing Python, ensure your system is up-to-date by running:

sudo apt update
sudo apt upgrade

This will fetch the latest package lists and install any available upgrades.

Method 1: Install using Deadsnakes PPA

The recommended way to install Python 3.9 on Linux Mint 20 is via the Deadsnakes PPA repository maintained by Felix Krull. This contains up-to-date builds for newer Python versions.

Here are the steps to add Deadsnakes PPA and install Python 3.9:

1. Install prerequisites:

    sudo apt install software-properties-common

   The software-properties-common package provides the add-apt-repository command used to add PPAs.

2. Add Deadsnakes PPA:

    sudo add-apt-repository ppa:deadsnakes/ppa

   When prompted press Enter to continue:

   

3. Once the repository is enabled, update package list:

    sudo apt update

4. Install Python 3.9 and its dependencies:

    sudo apt install python3.9

   Type y when asked to continue and install the packages.

5. Verify Python 3.9 installed correctly:

    python3.9 --version

   This will print the version installed:

    Python 3.9.0

That‘s it! Python 3.9 is now installed and ready to use on your Linux Mint 20 system.

Method 2: Build from Source Code

Building Python from source is more complex but can be useful if you need specific customizations or optimizations. Here is an overview of the process:

Install Build Tools and Dependencies

Python relies on various system libraries and tools to build correctly. Run the following to install them:

sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget

Download Python 3.9 Source Code

Use wget to download the latest Python 3.9 tarball (tgz compressed file):

wget https://www.python.org/ftp/python/3.9.0/Python-3.9.0.tgz

Verify using ls and you should see the .tgz file downloaded.

Extract Source Files

Use tar to extract the downloaded tarball:

tar -xf Python-3.9*.tgz

This will decompress the content into a new Python-3.9.0 directory.

Configure and Build

cd Python-3.9.0
./configure --enable-optimizations
make -j 8

This runs the configure script with performance optimizations enabled, then runs make to build the Python binary and libraries using 8 CPU cores for faster compilation.

Install Python 3.9

sudo make altinstall

The altinstall target prevents overwriting the default system Python 3 binary.

Verify Installation

Check that Python 3.9 is available by running:

python3.9 --version

And there we have it installed from source!

Next Steps After Installing Python 3.9

Now that you have a fresh Python 3.9 setup, here are some next steps to take:

• Update pip – Python‘s package manager with python3.9 -m pip install --upgrade pip
• Setup virtual environments – Create isolated Python environments for your projects with venv or pip install virtualenv
• Install IPython – An improved Python REPL shell with python3.9 -m pip install ipython
• Browse the stdlib – Explore the extensive Python standard library for useful modules like os, sys, datetime and many more

Also check out our other Linux Mint tutorials and guides for managing Python packages, building projects, and more!

Troubleshooting Guide

Here are solutions for common problems faced during Python 3.9 installation on Linux Mint:

Dependency errors

If you get errors like "package xyz has no installation candidate" while installing Python packages, run:

sudo apt --fix-broken install

This will attempt to fix any broken dependencies.

Permission errors

Using sudo is required for installing packages globally. If you get "Permission denied" errors, rerun the commands with sudo.

Old Python version still default

To make Python 3.9 the default instead of the older system Python 3.x:

1. Find location of the binaries: which python3 and which python3.9
2. Back up original binary: sudo mv /usr/bin/python3 /usr/bin/python3-old
3. Symlink new version: sudo ln -s $(which python3.9) /usr/bin/python3

Now python3 will point to Python 3.9.

Can‘t find Python modules

The altinstall method places binaries in a separate location like /usr/local/bin/python3.9 rather than /usr/bin. So you may need to use the full path for running scripts, pip installing packages globally, etc.

Or add the directory with Python 3.9 to your $PATH:

export PATH="/usr/local/bin:$PATH"

Stale cache issues

If you run into issues with old cached Python packages or corrupt downloads, run:

sudo apt clean
rm -rf ~/.cache/pip

This wipes the OS package cache and pip download cache to resolve such problems.

I hope these troubleshooting tips help you in keeping your Python install happy and running smoothly!

Conclusion

There are a few different ways to get the latest Python 3.9 on Linux Mint 20. The Deadsnakes PPA provides a simple and reliable installation. While compiling from source code enables further customization for power users.

Now that you have Python 3.9 ready, you can take advantage of the many new features and speed improvements it brings. Be sure to also brush up on virtual environments, pip/package management, and other Python best practices.

Let me know in the comments if you have any other questions on getting set up with Python 3.9!