All steps required to create or update the projects conda environment are run automatically running:

cenv

ATTENTION:

If you use cenv, each environment should only be created, updated and modified using cenv! This means the commands conda install, conda remove are not used anymore. Changes of the dependencies of the environment are defined inside the meta.yaml and are applied by using cenv.

This means:

• new dependency required => add it in meta.yaml and run cenv.
• dependency not needed anymore => remove it from meta.yaml and run cenv.
• need of another version of dependency => change the version of dependency in meta.yaml and run cenv.

The required information about the projects conda environment are extracted from the meta.yaml. This meta.yaml should be located inside the project folder at ./conda-build/meta.yaml. The project-configuration is defined in the extra section of the meta.yaml. There you can define the name of the projects conda-environment at env_name. Also you can define requirements only needed during development but not to be included into the resulting conda package. These requirements have to be defined in the dev_requirements-section.

All other parts of the meta.yaml have to be defined as default.

A meta.yaml valid for cenv should look like the following:

    {% set data = load_setup_py_data() %}

    package:
        name: "example_package"
        version: {{ data.get("version") }}

    source:
        path: ..

    build:
        build: {{ environ.get('GIT_DESCRIBE_NUMBER', 0) }}
        preserve_egg_dir: True
        script: python -m pip install --no-deps --ignore-installed .

    requirements:
        build:
          - python 3.6.8
          - pip
          - setuptools
        run:
          - python 3.6.8
          - attrs >=18.2
          - jinja2 >=2.10
          - ruamel.yaml >=0.15.23
          - six >=1.12.0
          - yaml >=0.1.7
          - marshmallow >=3.0.0rc1*

    test:
        imports:
            - example_package

    extra:
        env_name: example
        dev_requirements:
            - ipython >=7

ATTENTION:

In the requirements-run-section the minimal version of each package has to be defined! The same is required for the dev_requirements-section. Not defining a version will not create or update a conda-environment, because this is not the purpose of the conda-usage. The validity of the meta.yaml is checked in cenv using the marshmallow package. You can additionally add upper limits for the version like the following: - package >=0.1,<0.3

If cenv is run the environment is created / updated from the definition inside this meta.yaml. The creation of the backup of the previous environment ensures to undo changes if any error occurs during recreation of the environment.

ATTENTION:

cenv can only update the environment if it is not activated. So ensure the environment to be deactivated before running cenv.

Per default exporting the conda environment definition into an environment.yml is turned off. If you want to turn this functionality on you need to modify your ~/.config/cenv.yml as described in configuration.

Example for the output of the cenv command:

    ┣━━ Cloning existing env as backup ...
    ┣━━ Removing existing env ...
    ┣━━ Creating env ...
    ┣━━ Removing backup ...
    ┗━━ Exporting env to environment.yml ...