Python and Packages

Python

To get start with python is very easy. But to come back to a project and let it run again can hurt. This should be a small introduction how to handle python environements.

It is important for the following steps, to have now activated environments. For example if you using conda (you can see it in the terminal - (base) ), then you should deactivate it. Maybe in the past you had some troubles... It can be a good idea to clean the base in conda.

Conda deactivate: conda deactivate
Conda actiavate (base): conda activate
Conda clean (base): conda clean --all

For checking, which pyhton version is in use: which python

Python versions

As we all, also Python is developping. Some packages are developped for the newest python and a specific time but not updated for the newest python versions. This can be a problem when you want to use this package, but you just installed the newest version.

The solution is to use a virtual environment (for example conda, pipenv, ect.).

In this case we will have a look for pyenv (the easier way to work with python versions).

Pyenv

Installation

To install pyenv you can use the automatic installer (tested with Ubuntu):
curl https://pyenv.run | bash

After that you have to add the following lines to your vim ~/.bashrc fileend:

#Pyenv loader
export PYENV_ROOT="$HOME/.pyenv"
[[ -d $PYENV_ROOT/bin ]] && export PATH="$PYENV_ROOT/bin:$PATH"
eval "$(pyenv init -)"

# Load pyenv-virtualenv automatically
eval "$(pyenv virtualenv-init -)"

To take this changes into effect you have to restart your terminal or run source ~/.bashrc. Now it is ready to go.

Useful commands

command	description
`pyenv install --list`	all possible python versions to install.
`pyenv install <version>`	install the choosen from --list. This can take a while...
`pyenv versions`	shows all installed environments and the active one
`pyenv`	help site
`pyenv global <system>`	Don't use this, if you not sure what you are doing. We will use poetry for the python versions.
`pyenv local <system>`	If poetry can't find your version. Use this to load the rigth version and the use poetry.

Poetry

Poetry takes care of the python versions and the packages. All this is handled in a single *.toml file. Changes can be done in this file, but mainly it is recommended to use the terminal.

Installation

Pip is the package manager for python. For poetry it is recommended to install it with pipx, which takes care of the packages globaly.

Install pipx

sudo apt update
sudo apt install pipx
pipx ensurepath

install poetry

pipx install poetry

Useful commands

command	description
`poetry install`	Takes the *.toml file and installs all the packages. Creates the poetry.lock file.
`poetry init`	This folder will set up to use a virtual environement with poetry.
`poetry new <projectname>`	Makes the folder with the files in it.
`poetry add <pythonpackage>`	Add a package to your project.
`poetry update`	For added packages, it is recommended to update them after that.
`poetry env use <pythonversion>`	Change python version.
`poetry run <python script.py>`	Run your code in poetry.
`poetry show`	Poetry show packages from environment.

poetry install is the same as poetry update if there's no poetry.lock file. It's only slightly more convenient to install directly from the poetry.lock file if you don't want to update dependencies. poetry lock creates a poetry.lock file, but does not install packages. It can be useful in groupworks, that the poetry.lock stays "unchanged". So all collaborators are sure, it works with the defined packages.

Backlinks

2024-02-29