Choose languages for your environment#

You can define many different languages in your configuration files. This page describes how to use some of the more common ones.

Python#

Your environment will have Python (and specified dependencies) installed when you use one of the following configuration files:

  • requirements.txt

  • environment.yml

By default, the environment will have Python 3.10.

Specify a version of Python#

To specify a specific version of Python, you have two options:

  • Use environment.yml. Conda environments let you define the Python version in environment.yml. To do so, add python=X.X to your dependencies section, like so:

    name: python 2.7
dependencies:
  - python=2.7
  - numpy

  • Use runtime.txt with requirements.txt. If you are using requirements.txt instead of environment.yml, you can specify the Python runtime version in a separate file called runtime.txt. This file contains a single line of the following form:

    python-X.X

    For example:

    python-3.6

Supported versions of Python#

Repo2docker officially supports the following versions of Python:

  • 3.11 (added in 2023)

  • 3.10 (added in 2022, default in 2023)

  • 3.9 (added in 2021)

  • 3.8 (added in 0.11)

  • 3.7 (added in 0.7, default in 0.8)

  • 3.6 (default in 0.7 and earlier)

  • 3.5

  • 2.7

Additional versions may work, as long as the base environment can be installed for your version of Python. The most likely source of incompatibility is if one of the packages in the base environment is not packaged for your Python, either because the version of the package is too new and your chosen Python is too old, or vice versa.

If an old version of Python is specified (3.6 or earlier in 2023), a separate environment for the kernel will be installed with your requested Python version. The notebook server will run in the default Python 3.10 environment. That is, your notebooks will run with Python 3.6, while your notebook server will run with Python 3.10.

These two environments can be distinguished with $NB_PYTHON_PREFIX/bin/python for the server and $KERNEL_PYTHON_PREFIX/bin/python for the kernel. Both of these environment variables are always defined, even when they are the same.

Starting in 2023, the default version of Python used when Python version is unspecified will be updated more often. Python itself releases a new version every year now, and repo2docker will follow, with the default Python version generally trailing the latest stable version of Python itself by 1-2 versions.

If you choose not to specify a Python version, your repository is guaranteed to stop working, eventually. We strongly recommend specifying a Python version (in environment.yml, runtime.txt, Pipfile, etc.)

The R Language#

repo2docker supports R, the open source RStudio IDE as well as Jupyter support for R with the IRKernel. To set it up, you need to create a runtime.txt file with the following format:

r-<version>-<YYYY>-<MM>-<DD>

This will provide you R of given version (such as 4.1, 3.6, etc), and a CRAN snapshot to install libraries from on the given date. You can install more R packages from CRAN by adding a install.R file to your repo. RStudio and IRKernel are installed by default for all R versions.

packagemanager.posit.co will be used to provide much faster installations via binary packages. For some packages, this might require you install underlying system libraries using apt.txt - look at the page for the CRAN package you are interested in at packagemanager.posit.co to find a list.

repo2docker stopped using the Microsoft mirror MRAN for older R versions after its shutdown in July, 2023.

Supported versions of R#

The default version of R is currently R 4.2. You can select the version of R you want to use by specifying it in the runtime.txt file.

We support R versions 3.4, 3.5, 3.6, 4.0, 4.1 and 4.2.

Julia#

To build an environment with Julia, include a configuration file called Project.toml. The format of this file is documented at the Julia Pkg.jl documentation. To specify a specific version of Julia to install, put a Julia version in the [compat] section of the Project.toml file, as described here: https://julialang.github.io/Pkg.jl/v1/compatibility/.

Supported versions of Julia#

All Julia versions since Julia 1.3 are supported via a Project.toml file, and this is the recommended way to install Julia environments.

Julia < 1.3 and the older Julia REQUIRE file is no longer supported because required infrastructure has been removed.

Languages not covered here#

If a language is not “officially” supported by a build pack, it can often be installed with a postBuild script. This will run arbitrary bash commands, and can be used to download / install a language.

Using multiple languages at once#

It may also be possible to combine multiple languages in a single environment. The details on how to accomplish this with all possible combinations are outside the scope of this guide. However we recommend that you take a look at the Multi-Language Demo repository for some inspiration.