How to automatically create a environment.yml that works with repo2docker

This how-to explains how to create a environment.yml that specifies all installed packages and their precise versions from your environment.

The challenge

conda env export -f environment.yml creates a strict export of all packages. This is the most robust for reproducibility, but it does bake in potential platform-specific packages, so you can only use an exported environment on the same platform.

repo2docker uses a linux based image as the starting point for every docker image it creates. However a lot of people use OSX or Windows as their day to day operating system. This means that the environment.yml created by a strict export will not work with error messages saying that certain packages can not be resolved (ResolvePackageNotFound).

The solution

Export your explicit install commands

To get a minimal environment.yml that only contains the packages you explicitly installed run conda env export --from-history -f environment.yml. We recommend that you use this option to create your environment.yml. The resulting environment.yml then contains a loose pinning of the versions used, e.g. pandas=0.25 if you explicitly requested this pandas version on installation. If you didn’t list a version constraint during installation, it will also not be listed in your environment.yml.

While this approach doesn’t lead to perfect reproducibilty, it will contain just the same packages as if you would recreate the enviroment with the same commands again today.

Strict version export

Follow this procedure to create a strict export of your environment that will work with repo2docker and sites like mybinder.org.

We will launch a terminal inside a basic docker image, install the packages you need and then perform a strict export of the environment.

  1. install repo2docker on your computer by following Installing repo2docker

  2. in a terminal launch a basic repository repo2docker https://github.com/binder-examples/conda-freeze inside repo2docker

  3. open the URL printed at the end in a browser, the URL should look like http://127.0.0.1:61037/?token=30e61ec80bda6dd0d14805ea76bb59e7b0cd78b5d6b436f0

  4. open a terminal by clicking “New -> Terminal” next to the “Upload” button on the right hand side of the webpage

  5. install the packages your project requires with conda install <yourpackages>

  6. use conda env export -n root to print the environment

  7. copy and paste the environment you just printed into a environment.yml in your projects repository

  8. close your browser tabs and exit the repo2docker session by pressing Ctrl-C.

This will give you a strict export of your environment that precisely pins the versions of packages in your environment based on a linux environment.

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