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

Date: March 22, 2021

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/

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.

[code]
  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.

[code]
  # 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.

[code]
  conda create -n my-project python=3.9 -y

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

[code]
  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.

[code]
  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.

[code]
  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.

[code]
  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

[code]
  source activate $(basename $PWD) || condanew

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

Final Result
────────────

### Conda

[code]
  direnv edit .

[code]
  #!/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.

[code]
  #!/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