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Installing python

Installing python 3.8 on Ubuntu 20.04.5

First, update and upgrade:

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sudo apt update && sudo apt upgrade

Add PPA for Python old versions. The old versions of Python such as 3.9, 3.8, 3.7, and older are not available to install using the default system repository of Ubuntu 22.04 LTS Jammy JellyFish or 20.04 Focal Fossa. Hence, we need to add a PPA offered by the “deadsnakes” team to get the old archived Python versions easily.

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sudo apt install software-properties-common

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sudo add-apt-repository ppa:deadsnakes/ppa

# If you get this error:
AttributeError: NoneType object has no attribute people
# Try Installing  python3-launchpadlib 
sudo apt-get install  python3-launchpadlib

Check python versions you want. Syntax:

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sudo apt-cache policy python<version>

In my case:

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sudo apt-cache policy python3.9

Install the version you want:

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sudo apt install python3.9

Set up a default version in your system:

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# Checkout existing versions
ls /usr/bin/python*

# Also, let's check out  whether any version is configured as python alternatives or not. For that run:
sudo update-alternatives --list python

# If the output is: “update-alternatives: error: no alternatives for python”. Then it means there are no alternatives that have been configured, hence let’s do some:
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.9 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.10 2
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.8 3

# Switch the default Python version 
sudo update-alternatives --config python

Other methods

No very orthodox but:

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# Check current Python pointer
ls -l /usr/bin/python

# Check available Python versions**
ls -l /usr/bin/python*

# Unlink current python version**
cd /usr/bin
sudo unlink python

# Select required python version and lin to python command**
sudo ln -s /usr/bin/python2.7 python

# Confirm change in pointer**
ls -l /usr/bin/python

Installing python in Kali

If you are on Ubuntu 19.10 (or any other version unsupported by the deadsnakes PPA, like it's the case of Kali), you will not be able to install using the deadsnakes PPA.

First, install development packages required to build Python.

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

Then download the tarball and extract it:

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wget https://www.python.org/ftp/python/3.9.19/Python-3.9.19.tar.xz
tar -xf Python-3.9.19.tar.xz

Once the Python tarball has been extracted, navigate to the configure script and execute it in your Linux terminal with:

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cd Python-3.9.19
./configure

The configuration may take some time. Wait until it is successfully finishes before proceeding.

If you want to create an alternative install for python, start the build process: 

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sudo make altinstall

If you want to replace your current version of Python with this new version, you should uninstall your current Python package using your package manager (such as apt or dnf) and then install:

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sudo make install

Installing pip

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python3 -m pip install pip

If you get error: externally-managed-environment, then the solution is create an environment. As the message explains, this is actually not an issue with Python itself, but rather your Linux distribution (Kali, Debian, etc.) implementing a deliberate policy to ensure you don't break your operating system and system packages by using pip (or Poetry, Hatch, PDM or another non-OS package manager) outside the protection of a virtual environment.

Creating a virtual environment

See virtual Environments.

Switch python versions

See pyenv.

Last update: 2024-03-29
Created: January 1, 2023 21:59:36