Installing Python on Ubuntu =========================== .. warning:: If you change or try to tinker with the default Python version of Ubuntu, your system will most likely **BREAK COMPLETELY**. Do not play around with the default Python installation, because Ubuntu depends on it to work properly (or work at all). In Ubuntu, Python is already installed! In fact, Ubuntu would not work without it. Let's check its version by running .. code-block:: console python3 --version which should output .. code-block:: console Python 3.12.3 If the :code:`3.12` part of your version is different, this tutorial might not work for you. Please make sure to use the default Python in your Ubuntu. .. warning:: Note that the command is :program:`python3` and not :program:`python`. In fact, the result of .. code-block:: console python is .. code-block:: console Command 'python' not found, did you mean: command 'python3' from deb python3 command 'python' from deb python-is-python3 A quick Python check -------------------- Run .. code-block:: console python3 which should output something similar to .. code-block:: console Python 3.12.3 (main, Jun 18 2025, 17:59:45) [GCC 13.3.0] on linux Type "help", "copyright", "credits" or "license" for more information. >>> in particular, if the :code:`GCC 13` is different, then this tutorial might not work for you. As you already know, to exit the `interactive shell `_ you can use :kbd:`CTRL+D` or type :code:`quit()` and press :kbd:`ENTER`. Some Python packages must be installed through :program:`apt` ------------------------------------------------------------- .. warning:: Aside from these packages that you **MUST** install from :program:`apt`, it is best to use :program:`venv` and :program:`pip` to install packages only for your user without using :code:`sudo`. For some Python packages to work well with the default Python in Ubuntu, they must be installed through :program:`apt`. If you deviate from this, you can cause issues that might not be easy to recover from. For the purposes of this tutorial, let us install :code:`pip` and :code:`venv` .. code-block:: console sudo apt update sudo apt install -y python3-pip python3-venv .. _Isolate your environment with a venv: When you want to isolate your environment, use :program:`venv` -------------------------------------------------------------- .. warning:: At the time of this writing, there was no support for :program:`venv` on ROS2 `(More info) `_. Until that is handled, we are not going to use :program:`venv` for the ROS2 tutorials. However, we will use :program:`venv` to protect our ROS2 environment from these Python preamble tutorials. Using :program:`venv` (`More info `_) is quite straightforward. Create a :file:`venv` ^^^^^^^^^^^^^^^^^^^^^ .. code-block:: console cd ~ python3 -m venv ros2tutorial_venv where the only argument, :code:`ros2tutorial_venv`, is the name of the folder in which the :code:`venv` will be created. Activate a :file:`venv` ^^^^^^^^^^^^^^^^^^^^^^^ Whenever we want to use a :file:`venv`, it must be explicitly activated. .. code-block:: console cd ~ source ros2tutorial_venv/bin/activate The terminal will change to have the prefix :code:`(ros2tutorial_venv)` to let us know that we are using a :file:`venv`, as follows .. code-block:: console (ros2tutorial_venv) murilo@murilos-toaster:~$ Deactivate a :file:`venv` ^^^^^^^^^^^^^^^^^^^^^^^^^ To deactivate, run .. code-block:: console deactivate We'll know that we're no longer using the :code:`ros2tutorial_venv` because the prefix will disappear back to .. code-block:: console murilo@murilos-toaster:~$ Installing libraries -------------------- .. warning:: In these tutorials, we rely either on :program:`apt` or :program:`pip` to install packages. There are other package managers for Python and plenty of other ways to install and manage packages. They are, in general, not compatible with each other so, like cleaning products, **DO NOT** mix them. .. hint:: Using :code:`python3 -m pip` instead of calling just :code:`pip` allows more control over which version of :program:`pip` is being called. The need for this becomes more evident when several Python versions have to coexist in a system. As an example, let us install the best robot modeling and control library ever conceived, `DQ Robotics `_. First, we activate the virtual environment .. code-block:: console cd ~ source ros2tutorial_venv/bin/activate then, we install .. code-block:: console python3 -m pip install dqrobotics --break-system-packages which will result in something similar to (might change depending on future versions) .. code-block:: console Collecting dqrobotics Downloading dqrobotics-25.4.0a17-cp312-cp312-manylinux2014_aarch64.whl.metadata (2.9 kB) Requirement already satisfied: numpy in /usr/lib/python3/dist-packages (from dqrobotics) (1.26.4) Downloading dqrobotics-25.4.0a17-cp312-cp312-manylinux2014_aarch64.whl (512 kB) ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 512.5/512.5 kB 14.0 MB/s eta 0:00:00 [...] Installing collected packages: dqrobotics Successfully installed dqrobotics-25.4.0a17 Removing libraries (installed with :program:`pip`) -------------------------------------------------- We can remove the library we just installed with .. code-block:: console python3 -m pip uninstall dqrobotics --break-system-packages resulting in .. code-block:: console Found existing installation: dqrobotics 25.4.0a7 Uninstalling dqrobotics-25.4.0a7: Would remove: /usr/local/lib/python3.12/dist-packages/dqrobotics-25.4.0a7.dist-info/* /usr/local/lib/python3.12/dist-packages/dqrobotics/* Proceed (Y/n)? .. hint:: If in the terminal a question is made, the option with an uppercase letter, in this case :kbd:`Y`, will be the default. If you want the default, just press :kbd:`ENTER`. Then, press :kbd:`ENTER`, which results in .. code-block:: console Successfully uninstalled dqrobotics-25.4.0a7 When using :program:`pip`, do **NOT** use :code:`sudo` ------------------------------------------------------ Using :code:`sudo` without knowing what one is doing is *the* easiest way to wreak havoc in a Ubuntu installation. Even seemingly innocuous operations such as copying files with :code:`sudo` can cause irreparable damage to your Ubuntu environment. When installing Python packages that are not available on :program:`apt`, use :program:`pip`.