The proper way to install Python libraries and applications is to install them in a Python virtual environment whenever possible (the exceptions to this rule are quite rare).

The error message describes two common ways to accomplish this: either by creating a virtual environment yourself, or for applications, by using pipx—a tool which will create a virtual environment for you and install the application in that virtual environment.

pipx is strongly recommended for installing applications, i.e., when you will primarily use the installed code from the command line. On Debian systems and Debian-based systems such as Ubuntu, you can install pipx using apt, and then use pipx to install the application:

apt install pipx
pipx install some-python-application

For libraries, i.e., when you will use the code primarily by importing it in your own projects. Typically, you should create a virtual environment yourself. You can do this with venv from the standard library:

python -m venv my-venv
my-venv/bin/pip install some-python-library

See also this answer on a duplicate question for more details.

(Commonly, your own project may need several libraries. Make one virtual environment and install the libraries that your project needs side by side in that virtual environment.)

If you know you don’t need to use your system long-term (e.g. because you’re working in a container or CI environment like Docker or GitHub Actions), and you're still sure that you want to install packages "system-wide" and risk breaking your system (for example, by overwriting libraries that were part of tools written in Python that came with your system), Pip needs to be given permission to do so.

There are a few ways to do this:

• For a single use of pip, add the --break-system-packages argument to the command.

• Add these lines to ~/.config/pip/pip.conf (this will enable every future run of Pip to break system packages:

  [global]
  break-system-packages = true
  

• Use Pip's config command to edit the above file (credit to The Matt from the comments):

  python3 -m pip config set global.break-system-packages true
  

Theoretically, removing or renaming the "marker" file (/usr/lib/python3.x/EXTERNALLY-MANAGED) would also disable the block, but this is a bad idea. The file was put there for a reason, and it's at least as easy to use the intended mechanisms instead.

There's a good article on OMGUbuntu about this: 3 Ways to Solve Pip Install Error on Ubuntu 23.04

Here's the summary. There are three ways to approach this problem:

1. Install the Python package using APT

For instance, if you want to install the requests Python library, you can install it using APT instead, like this:

sudo apt install python3-requests

This will install this library system-wide.

Not all packages available on PyPI have been packaged and included in the Debian/Ubuntu repositories, so this method won't work for some packages.

Or: 2. Create a virtual environment using venv or virtualenv

Make sure venv is installed by running:

sudo apt install python3-venv

To create a new virtual environment in a directory named .venv, run:

python3 -m venv .venv

To activate this virtual environment (which modifies the PATH environment variable), run this:

source .venv/bin/activate

Now you can install a library like requests in this virtual environment:

pip install requests

The files will get installed under the .venv/ directory.

If you want to leave the virtual environment, you can run:

deactivate

If you don't want to run source .venv/bin/activate and deactivate, then you can run the executable by prefixing its path, like this:

 $ .venv/bin/pip install requests
 $ .venv/bin/python3
 >>> import request
 >>> help(requests)

Or: 3. Use pipx

pipx lets you install and run Python applications in isolated environments. This is the recommended way to install PyPI packages that represent command-line applications.

To install pipx, run:

 sudo apt install pipx

pipx needs ~/.local/bin/ to be in your PATH. You can automatically modify your shell configuration (such as ~/.bashrc) to modify PATH appropriately by running:

 pipx ensurepath

(You may need to close your terminal application and open it again for the changes to take effect.)

Now you can install a package from PyPI, like this:

 pipx install pycowsay

And you can run the command that you just installed, like this:

$ pycowsay Mooo!

  -----
< Mooo! >
  -----
   \   ^__^
    \  (oo)\_______
       (__)\       )\/\
           ||----w |
           ||     ||

As you can see, pipx installed a symlink in ~/.local/bin/ to the executable in a virtual environment:

$ ls -l ~/.local/bin/pycowsay
lrwxrwxrwx 1 flimm flimm 50 May 24 11:19 /home/flimm/.local/bin/pycowsay -> /home/flimm/.local/pipx/venvs/pycowsay/bin/pycowsay*

Or: 4. Pass --break-system-packages flag:

If you want to ignore the warning, you can pass the --break-system-packages flag:

pip install --break-system-packages --user <foobar>

This method is not recommended, because you may find yourself with mysterious broken installations of Python packages months or years later, after you've forgotten that you used --break-system-packages and installed other conflicting Python packages.