Introduction

On Ubuntu, the python command historically pointed to Python 2. Modern Ubuntu versions (20.04+) no longer ship Python 2, but the python command may still be absent or misconfigured. Setting Python 3 as the default python involves using Ubuntu's update-alternatives system or creating a virtual environment. Changing the system-level python symlink carelessly can break system tools like apt and gnome-terminal that depend on specific Python versions.

Check Current Python Setup

1# Check what "python" points to
2python --version
3# bash: python: command not found  (common on Ubuntu 20.04+)
4
5# Check Python 3
6python3 --version
7# Python 3.10.12
8
9# Check all installed Python versions
10ls /usr/bin/python*
11# /usr/bin/python3  /usr/bin/python3.10  /usr/bin/python3.11
12
13# Check if alternatives are configured
14update-alternatives --list python
15# update-alternatives: error: no alternatives for python

Method 1: update-alternatives (Recommended)

The update-alternatives system lets you manage multiple versions of a command with configurable priority.

1# Register Python 3.10 as an alternative for "python"
2sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.10 1
3
4# Register Python 3.11 if also installed
5sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.11 2
6
7# The number at the end is the priority — higher wins in auto mode
8
9# Switch between versions interactively
10sudo update-alternatives --config python
11#   Selection    Path                 Priority   Status
12# ------------------------------------------------------------
13# * 0            /usr/bin/python3.11   2          auto mode
14#   1            /usr/bin/python3.10   1          manual mode
15#   2            /usr/bin/python3.11   2          manual mode
16
17# Verify
18python --version
19# Python 3.11.x

Method 2: Shell Alias

For a per-user solution that does not affect the system, add an alias to your shell configuration.

1# Add to ~/.bashrc or ~/.zshrc
2alias python=python3
3alias pip=pip3
4
5# Reload the shell config
6source ~/.bashrc
7
8# Verify
9python --version
10# Python 3.10.12

This only affects interactive shells — scripts that use #!/usr/bin/env python will not pick up the alias.

Method 3: Symlink (Quick but Risky)

1# Create a symlink manually
2sudo ln -s /usr/bin/python3 /usr/bin/python
3
4# Verify
5python --version
6# Python 3.10.12

This is simple but update-alternatives is preferred because it tracks the configuration and allows easy switching.

Method 4: Virtual Environments (Best for Projects)

For project-specific Python versions, use virtual environments instead of changing the system default.

1# Create a virtual environment with Python 3.11
2python3.11 -m venv myproject_env
3
4# Activate it
5source myproject_env/bin/activate
6
7# Now "python" points to Python 3.11 within this environment
8python --version
9# Python 3.11.x
10
11# Deactivate when done
12deactivate

Fixing pip After Changing Python Version

After changing the default Python, pip may also need updating.

1# Install pip for the new default Python
2python -m ensurepip --upgrade
3
4# Or install via apt
5sudo apt install python3-pip
6
7# Verify pip points to the correct Python
8pip --version
9# pip 23.x from /usr/lib/python3/dist-packages/pip (python 3.11)
10
11# If pip still points to the old version, use:
12python -m pip install --upgrade pip

Common Pitfalls

• Breaking system tools by changing the system Python: Ubuntu system utilities like apt, gnome-terminal, and do-release-upgrade depend on the system Python. Removing Python 3.x or forcibly replacing /usr/bin/python3 can make these tools fail. Never remove the system Python package. Use update-alternatives which manages symlinks safely.
• Using sudo ln -sf to overwrite /usr/bin/python3: Overwriting the python3 symlink (not python) can break apt and package management. Only create or modify the python symlink — leave python3 managed by the system package manager.
• Alias not working in scripts or cron jobs: Shell aliases defined in ~/.bashrc only apply to interactive shells. Scripts invoked by cron, systemd, or #!/usr/bin/env python shebangs will not see the alias. Use update-alternatives or modify the shebang to #!/usr/bin/env python3.
• Forgetting to update pip after switching versions: After changing the default Python, pip may still be associated with the old version. Always run python -m pip install --upgrade pip after switching to ensure pip installs packages for the correct Python.
• Not using deadsnakes PPA for newer Python versions: Ubuntu's default repositories may not have the latest Python. To install Python 3.12+ on Ubuntu 22.04, add the deadsnakes PPA: sudo add-apt-repository ppa:deadsnakes/ppa && sudo apt update && sudo apt install python3.12.

Summary

• Use update-alternatives --install to register Python versions and --config to switch between them
• Add alias python=python3 to ~/.bashrc for a per-user, non-system-affecting solution
• Use virtual environments for project-specific Python version isolation
• Never remove or overwrite /usr/bin/python3 — it is managed by the system package manager
• Always update pip after changing the default Python version