Python

Python is a high-level, interpreted general-purpose programming language, Created by Guido van Rossum in 1991.

In Python, white-space has significance in scope.

Python2 (eol 2020) and Python3 (from 2008) have an incompatible syntax. By default the python interpreter is called with /usr/bin/python3, but a symlink can make python be called without the need to specify a version.

sudo apt install python-is-python3

/usr/bin/python is a symlink to /usr/bin/python3 which in turn is a symlink to /usr/bin/python3.13

python -VV
Python 3.13.12 (main, Feb  4 2026, 15:06:39) [GCC 15.2.0]

PIP

PIP is the Python installation manager (and so is PIPX and UV)

https://pip.pypa.io/en/stable/user_guide/

pip config list -v

pip has an optional configuration file

/etc/pip.conf
[global]
target = /usr/lib/python3/dist-packages

Python packages can be installed with the distribution

apt install python3-numpi
apk add py3-numpi

This will pull the package from PYPI and install the package in the dist-pacakges. It's also possible to install your own packages in the site-packages

/usr/lib/python3/dist-packages/
~/.local/lib/python3.13/site-packages/

To override version numbers and avoid dependency hell, A virtual environment can separate the versions in use, I never use virtual environments, I manage the dependencies instead

python3 -m venv myenv
source myenv/bin/activate

PIP can be installed as a distribution package or via a get-pip script

apt install python3-pip
wget https://bootstrap.pypa.io/get-pip.py

PIP can run as python module with

python -m pip
pip list -v

To prevent apt and pip to install incompatible versions, an externally-managed file prevents packages from being installed with pip unless --break-system-packages is given or the check is removed

sudo rm -f /usr/lib/python3.13/EXTERNALLY-MANAGED

The -v will show where the dependencies are installed and from which package manager they come from, personally I prefer the packages to be installed by pip, but some will come automatically with debian. They can be replaced by removing the package without removing the packages that depend on them and reinstalling them with pip

sudo dpkg --remove --force-depends python3-pygobject

To upgrade all pip packages

pip --disable-pip-version-check list --outdated --format=json | python -c "import json, sys; print('\n'.join([x['name'] for x in json.load(sys.stdin)]))" | xargs -n1 pip install -U

pythonists frown upon version upgrades, because some feel versions should be sticky and new software may introduce depenency incompatibilities (fear of change)

the setup.py contains minimum and maximum versions a module can require.

Advanced stuff

PYCACHE

Wheel

Compile to elf

Certbot

certbot --version

certbot plugins

sudo certbot certonly --dns-azure-config /etc/letsencrypt/azure.cfg -d build.domainname.com

certbot renew --dry-run

Certbot needs a plugin to do DNS validation against Azure DNS. Due to dependency updates, the version range that the plugin requires, the plugin is pegged to an old version of certbot. The original author is not updating these dependencies, nor is merging pull requests, not is answering issues in github.

https://github.com/terricain/certbot-dns-azure

The forks revolve around updating setup.py and snap-requirements.txt, changing between setting and removing upper limits, to avoid upwards incompatibilities.

This worked for me February 2026 for certbot 5.3.1

install_requires = [
    'azure-identity>=1.19.0,<2.0.0',
    'azure-mgmt-dns>=8.2.0,<9.0.0',
    'azure-core>=1.32.0,<2.0.0',
    'setuptools>=41.6.0',
    'certbot>=3.0',
]

pip install .

Deepdive

strace -f -e trace=openat,close,read certbot

which python3
/usr/bin/python3
ls -la /usr/bin/python3

ldd /usr/bin/python3.10
       linux-vdso.so.1 (0x00007ffd137b7000)
       libm.so.6 => /lib/x86_64-linux-gnu/libm.so.6 (0x00007f7b3f900000)
       libexpat.so.1 => /lib/x86_64-linux-gnu/libexpat.so.1 (0x00007f7b3f8cf000)
       libz.so.1 => /lib/x86_64-linux-gnu/libz.so.1 (0x00007f7b3f8b3000)
       libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x00007f7b3f68b000)
       /lib64/ld-linux-x86-64.so.2 (0x00007f7b3ffe3000)

/usr/bin/python3.10 -V
Python 3.10.6

/usr/bin/python3.10 -VV
Python 3.10.6 (main, Mar 10 2023, 10:55:28) [GCC 11.3.0]

python3 -c "import sys; print('\n'.join(sys.path))"

/usr/lib/python310.zip
/usr/lib/python3.10
/usr/lib/python3.10/lib-dynload
/usr/local/lib/python3.10/dist-packages
/usr/lib/python3/dist-packages
/usr/lib/python3.10/dist-packages

find /usr/lib/python3.10/ -name shutil*
/usr/lib/python3.10/shutil.py
/usr/lib/python3.10/__pycache__/shutil.cpython-310.pyc

python3-setuptools

PIP

which pip
~/.local/lib/python3.8/site-packages

pip config set global.index-url https://pypi.org/simple
python3 -m pip list

python3 -m pip freeze > requirements.txt
python3 -m pip install -r requirements.txt --upgrade

python -m pip install --upgrade pip
pip install numpy

pip install -U `pip list --outdated | awk 'NR>2 {print $1}'`
pip freeze --local | grep -v '^\-e' | cut -d = -f 1  | xargs -n1 pip install -U
pip --disable-pip-version-check list --outdated --format=json | python -c "import json, sys; print('\n'.join([x['name'] for x in json.load(sys.stdin)]))"

pip install --upgrade --upgrade-strategy eager

venv

pyinstaller --onefile --noconfirm --noconsole --clean --log-level=WARN -p . --strip hello.py