---
title: How to use virtual environments
date: 2022-06-19
lastmod: 2022-06-19
tags: code
Tags: [python, R, julia]
slug: using-virtual-environments
author: Samuel Ortion
lang: en
status: published
---

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.

```bash
sudo apt install python3-venv
```

And now you can create venvs for your project:

```bash
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:

```bash
source .venv/myproject/bin/activate
```

And deactivate it when you are done:

```bash
deactivate
```

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:

```bash
pip freeze > requirements.txt
```

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

```bash
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.
```R
install.packages("packrat")
```

And create your virtual environment with:

```R
packrat::init("myproject")
```

Similarly, you can then install packages:

```R
install.packages("dplyr")
```

And create a snapshot of your dependencies with:

```R
packrat::snapshot()
```

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:

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

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

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

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

```bash
venv .venv/myproject
```

And you can activate/deactivate it:

```bash
source .venv/myproject/bin/activate

deactivate
```

That's it ! 

## References

- [Python venv documentation](https://docs.python.org/3/library/venv.html)
- [Packrat documentation](https://rstudio.github.io/packrat/)
- [Julia venv documentation](https://juliapackages.com/p/virtualenv)