`pip3` - the Python package installer

pip install [-r requirements.txt] PACKAGE...  |  pip freeze  |  pip list  |  pip show PACKAGE  |  pip uninstall PACKAGE

Options you will use

install PKG: Install a package and its dependencies into the ACTIVE environment.
install -r FILE: Install everything listed in a requirements file.
freeze: Print installed packages as name==version lines - the format of requirements.txt.
list: Table of installed packages.
--break-system-packages: Override PEP 668 and install into the system interpreter. Do not.
--no-cache-dir: Disable the cache (~/.cache/pip).
-q, --quiet: Give less output.
-v, --verbose: Give more output.
--disable-pip-version-check: Do not check PyPI for a newer pip.
--no-cache-dir: Disable the cache (~/.cache/pip).
-q, --quiet: Give less output.
-v, --verbose: Give more output.
--disable-pip-version-check: Do not check PyPI for a newer pip.

$ pip install requests

Inside a venv: installs requests, urllib3, idna, certifi, charset-normalizer.

$ pip freeze > requirements.txt

Pin exactly what you have, so the next machine gets the same versions.

On Ubuntu 23.04 and later, pip on the system python3 fails with "error: externally-managed-environment". That is PEP 668 protecting the packages apt installed: mixing pip into /usr breaks apt-managed tools.

Try pip3 in a real terminal Free, in your browser - a real Ubuntu terminal to try it in, with missions that check your work.