Q: What is new_conda_env?

A: A new env from an existing one...

This (future) conda-forge package outputs a "lean" yaml either for an existing conda environment or for a new one when, for instance, a user wants to replicate an existing env but with a different kernel version. The "lean" qualifyer reflects both the smaller size of the yaml file: only the user-installed packages — and those listed in .condarc — appear along with the version-less listing of all dependencies - except for that of the (python) kernel.

• Caveats:
  • At the moment, python is the first (& only) kernel considered.
  • There is no guarantee that the new environment is satisfiable e.g. some packages in envA using python 3.x may not exist in envB using python 3.y. The statisfiability check is left to be done by conda at the moment of installation. Unfortunately, there is no -dry-run option for conda env create -f file.yml (see conda issue #7495), so the user must be prepared for possible fatal errors at creation time.

Use cases (only two listed)

1. Get a "nearly identical" env for a different python version You've created a conda environment, which you would like to re-create with a different python version, i.e. you would like to have the same packages for a new version of the kernel.

• Example: You have a current python 3.10 conda environment for GIS applications, geo310. When you learn that there is a package that does exactly what you had planned to do, you want to install it... Except, that package is using python 3.9, so you need to reproduce the python 3.10 environment to work with the lower version.

2. You want to show a succinct environment yaml file during your presentation. It's perfectly alright to display the full blown yaml file when reporting a bug, for example. However, you'd rather have a shorter file that displays all the packages you have explicitely installed at the comman line — using either conda or pip — but not their dependencies.

Limitations of the current conda env export command:

1. The usual conda env export > environment.yml or conda env export --no-builds > environment.yml commands fix all packages dependencies, so they will not work with another (python) kernel version.
2. Using the --from-history option, e.g.: conda env export --from-history > environment.yml is closer to what's needed because it lists all the packages you installed at the command line, but it excludes all pip installations!

Manual workaround

1. Create a "minimal" env_hist.yml file from an existing environment using the --from-history option
2. Create a "complete" env_nobld.yml file using the --no-builds option
3. Edit env_hist.yml:
   3.1 Change name to that of the new environment
   3.2 Insert the missing pip installations (minus version numbers) listed in env_nobld.yml in the dependencies list & change the python version to the new one (or insert a line for python if missing)
   3.3 Change the prefix line so that the path uses the new name
4. Save env_hist.yml, or 'save as' a better name hinting at the creation process, e.g. lean_env39_from_geo310.yml. (Note: env39 would be the default naming pattern if no name is provided for the new env.)

Solution implemented in new_conda_env:

=> The package automates the manual workaround.

Call example:

After installation of new_conda_env from conda-forge:

new-conda-env -old_ver 3.10 -new_ver 3.9 -env_to_clone ds310 -new_env_name ds39

User-supplied data:

1. old_ver: The old version of the kernel in (major[.minor] format)
2. new_ver: The new version of the kernel to use (major[.minor] format)
3. dotless_ver: Whether to remove version period in env names
4. env_to_clone: The name of the conda env to "quick-clone"
5. new_env_name (optional): The name for the new environment
6. kernel (optional): Default & only kernel implemented: python
7. display_new_yml (optional, True): Whether to display the new yml file
8. log_level (optional, 'ERROR'): for logging control

Note:

old_ver and new_ver can be the same in case you want to obtain a 'lean' yaml file for for an existing environment with the same version.

Output:

The final file is named using this pattern: f"lean_env{kernel[:2]}{new_ver}_from_{env_to_clone}.yml" using the default naming for the new env, or: f"lean_{new_env_name}_from_{env_to_clone}.yml" using the user-provided name.

Final file example:

The following command (base) >new-conda-env -old_ver 3.10 -new_ver 3.9 -env_to_clone ds310 will use an environment named "ds310" using python 3.10 to output a yaml file for a "lean" copy using python 3.9. The final file — on my Windows system — is:

name: envpy39
channels:
  - conda-forge
  - bioconda
  - pyviz
  - nvidia
  - defaults
dependencies:
  - python=3.9
  - pip
  - flake8
  - beautifulsoup4
  - matplotlib
  - seaborn
  - pandas
  - ipython
  - python-dotenv
  - black
  - python-graphviz
  - ipykernel
  - pygraphviz
  - scipy
  - ipywidgets
  - numpy
  - pytest
  - pylint
  - scikit-learn
  - dask
  - pyspark
  - pyarrow
  - defusedxml
  - setuptools
  - wheel
  - pip:
      - actdiag
      - blockdiag
      - blockdiagmagic
      - funcparserlib
      - matplotlib-venn
      - networkx
      - nwdiag
      - seqdiag
      - watermark
      - webcolors
prefix: C:\Users\<you>\miniconda3\envs\envpy39

TODO

[ x ] Create all needed processing functions
[ x ] cli: Create
[ x ] Add check in argparse: kernel version needs a dot
[ x ] Add tests
[ x ] Upload to conda-forge [ x ] Use pyproject.toml only [ ] FUTURE: Implement "incremental" env yaml creation -> new entry point [ ] Do same for julia, R kernels (if requested with enhancement issues)

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What's yaml (yml)?

"YAML is a data serialization format designed for human readability and interaction with scripting languages"

More about yaml and ruamel.yaml (used by conda)