How to use virtual environments

Posted on Sun 19 June 2022 in code

To not interfere with your os configuration and keep your project reproducible, you should use a virtual environment as long as possible.

Virtual environment are a way to isolate your project from the rest of the system, and to avoid dependencies conflicts.

Python Virtualenv

Lets start by installing the virtualenv package.

sudo apt install python3-venv

And now you can create venvs for your project:

python3 -m venv .venv/myproject

It is a good practice not to create a virtualenv with name "venv", but to use a name that reflects the project you are working on, in order to see directly in which venv you are working.

Now you can activate the virtualenv:

source .venv/myproject/bin/activate

And deactivate it when you are done:


One other way to create a virtualenv is to use the virtualenv command.

Once you installed python packages, you should create a snapshot of your project dependencies using:

pip freeze > requirements.txt

That way, you can allow other people to use your project and installi its dependencies with the following command:

pip install -r requirements.txt

You could also use conda, as a package manager, to create a virtualenv.

R Virtualenv

R also has its own virtualenv gestionnal system named packrat.

First install packrat with R.


And create your virtual environment with:


Similarly, you can then install packages:


And create a snapshot of your dependencies with:


The dependency list is available in packrat/packrat.lock.

Julia Virtualenv

Julia venv is very similar to Python venv.

First, you install the VirtualEnv package:

julia -e 'using Pkg; Pkg.add("VirtualEnv")'

And add ~/.julia/bin to your path:

julia -e 'using VirtualEnv; VirtualEnv.comonicon_install_path()'

Then you can use venv to create a virtualenv for your project:

venv .venv/myproject

And you can activate/deactivate it:

source .venv/myproject/bin/activate


That's it !