Python virtual environments with virtualenv

virtualenv is a convenient tool to install virtual environemnts. Part of it is already implemented in venv for python>=3.3.

Install virtualenv

virtualenv is a package of python so you can install via pip install. We could install virtualenv in a virtual environment and call it from there. Instead if you decide to use virtualenv for your projects the most common is to install it in the default interpreter, the global in pyenv or the default in the system /usr/local/bin/python3 (in MacOS).

Define a global python using pyenv, as an example we will use 3.11.2.

GLOBAL_PYTHON=3.11.2
pyenv global ${GLOBAL_PYTHON}

Install virtualenv on it and check the help (just to see that it works)

python -m pip install virtualenv
python -m virtualenv --help

Create virtual environment with virtualenv

Now create a virtual environment with a custom python version (assuming we use pyenv for managing the versions) and that you installed virtualenv in the global pyenv python manager. You need to point to the specific python binary version for your new environment, so first install the python version for your environment if you don’t have it

PYTHON_VERSION=3.12.4
pyenv install ${PYTHON_VERSION}

Make sure you are in the global python version in your pyenv, that’s where we installed virtualenv.

pyenv shell --unset
rm -rf .python-version

Now you are ready to create the virtual environment

PYTHON_PATH="$(pyenv root)/versions/$PYTHON_VERSION/bin/python"
virtualenv -p ${PYTHON_PATH} .venv

The environmet can be found now in .venv directory.

Activate and add dependencies

Activate it as usual with source .venv/bin/activate and install with pip, for instance pip install numpy. Then deactivate with deactivate and remove virtual environment by just deleting the directory .venv.

source .venv/bin/activate
pip install numpy

deactivate
rm -rf .venv