Python Virtual Environment

Virtual Environments allow Python packages to be installed in an isolated environment instead of installing them globally.

Options:

venv: available by default in Python 3.3 and later
virtualenv: needs to be installed, supports Python 2.7+ and Python 3.3+
conda: package, dependency and environment management for many languages

Recommendation

Use conda to create a development enviroment that requires a specific version of Python and other tools (e.g. C/C++ compiler) and runtime libraries.

Use venv to manage the required Python packages in a project.

Once the virtual environment is created, use conda or pip to install additional Python packages.

Conda

Most used command options

Configuration:

conda config --add channels conda-forge
conda config --set channel_priority strict
conda config --set auto_activate_base false
conda update conda python -y

Creating an enviroment with a specific version of Python:

conda create -n pta-py27 python=2.7
conda create -n pta python=3.10

Installing packages:

conda install jupyter

Get list of installed packages in the current selected environment:

conda list

Get list of installed packages in the current selected environment:

conda list -n pta

Exporting an environment compatible across systems:

conda env export --from-history -f environment.yml

Creating an enviroment from a configuration file:

conda env create -f environment.yml 

Updating an enviroment from a configuration file:

conda env update --prune -f enviroment.yml

Removing an environment (you must deactivate the enviroment first):

conda env remove -n pta-py27

Activating/deactiving an enviroment:

conda activate pta
conda deactivate

Updating/upgrading an enviroment:

conda update -n pta

VENV

Most used command options

Creating a virtual environment using the current selected Python version:

python -m venv venv

Activating/deactiving the virtual environment:

source ./venv/bin/activate
deactivate 

Updating/upgrading a virtual environment:

python -mvenv --upgrade venv

Removing an virtual enviroment (just delete the folder):

rm -rf ./venv