---
title: "Automatic Conda Environments"
description: "I have automated my process to create virtual environments in my python projects, here is how I did it."
date: 2021-03-22
published: false
tags:
  - python
template: blog-post
---


I have automated my process to create virtual environments in my python
projects, here is how I did it.

I've really been digging my new tmux session management setup. Now I have
leveled it up by adding direnv to my workflow. It will execute a shell script
whenever I cd into a directory. One thing I wanted to add to this was,
automatic activation of python environments whenever I cd into a directory, or
create a new environment if one does not exist.

[https://waylonwalker.com/tmux-nav-2021/](https://waylonwalker.com/tmux-nav-2021/){.hoverlink}

## Direnv

You can learn more about [direnv](https://direnv.net/) on their website. There
are several libraries that seem to do a similar concept, _run a bash script
when I cd into a directory_ direnv is the one that I chose to use, but you can
likely do the same concept in other ones.

### Installation

direnv is in many package repos, or can be installed from binary builds with a
one liner. See their [installation](https://direnv.net/docs/installation.html)
instructions for more information.

```bash
curl -sfL https://direnv.net/install.sh | bash
```

### .envrc

direnv works by executing the contents of known safe `.envrc` files. Here are
some of the basic commands to get you started.

```bash
# edit or create a new .envrc and flag it as allowed
direnv edit .

# flag a .envrc file as allowed or not
direnv allow .
direnv deny .

# reexecute a .envrc
direnv reload
```

## Conda

I most often use conda to manage my virtual environments. I dont use it to
`conda install` packages, but I really like the convenience of combinging the
python interpreter with the environment.

```bash
conda create -n my-project python=3.9 -y
```

> every time I start a new project I need to create a new environment

```bash
conda activate my-project
# or source depending on if conda init has been ran on the system
source activate my-project
```

> every subsequent time I start work in that project I need to remember to activate

### lazy

I'll admit that sometimes I get lazy and will use an existing environment with
similar dependencies. This kind of works in a pinch, but almost always I need
more packages and start trampling in that other projects environment.

## naming the environment

Since I want this process to be easily automated I chose to name my
environments after the name of the directory the project is in. In bash we can
get the current directory with `$PWD`, and trim it to just the directory name
with the `basename` command.

```bash
basename $PWD
```

> this will return the name of the current working directory

## condanew

I reates a short bash function that will create a new conda environment,
activate it, and install anything extra that the project needs.

```bash
condanew() {
    conda create -n $(basename $PWD) python=3.8 -y
    source activate $(basename $PWD)
    pip install lolcat
}
```

> This will create a new python environment named after the current directory.

### project install

Often I will modify the condanew function to install project specific things.
I leverage editable installs of projects I am working on quite extensively,
that's what the `-e` is.

```bash
condanew() {
    conda create -n $(basename $PWD) python=3.8 -y
    source activate $(basename $PWD)
    pip install -e ".[dev]"
    # or
    pip install -r requirements.txt
}
```

## Bash error handling

I dive deeper into this subject in this post about creating
[reusable-bash](https://waylonwalker.com/reusable-bash/#error-handling)
scripts. But to auto create the environment I am going to try to activate. If
it fails, create a new environment based on the name of the project.

[https://waylonwalker.com/reusable-bash/#error-handling](https://waylonwalker.com/reusable-bash/#error-handling){.hoverlink}

```bash
source activate $(basename $PWD) || condanew
```

> Try to activate the environment, if it fails make a new one.

## Final Result

### Conda

```bash
direnv edit .
```

```bash
#!/bin/bash
# shortcut for creating new conda environments based on the current working directory
condanew() {
    conda create -n $(basename $PWD) python=3.8 -y
    source activate $(basename $PWD)
    pip install lolcat
}
echo $(basename $PWD) | lolcat
source activate $(basename $PWD) || condanew
```

### Venv

Here is a modified version using venv from the standard library.

```bash
#!/bin/bash
# shortcut for creating new virtual environments
venvnew() {
    python -m venv .venv
    source .venv/bin/activate
    pip install lolcat
}
echo $(basename $PWD) | lolcat
source .venv/bin/activate || venvnew
```