developers.home-assistant/docs/creating_component_deps_and_reqs.md

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Requirements & Dependencies

Home Assistant allows components and platforms to specify their dependencies and requirements using the variables DEPENDENCIES and REQUIREMENTS. Both are lists that contain strings.

Dependencies

Dependencies are other Home Assistant components that should be setup before the platform is loaded. An example is the MQTT sensor component, which requires an active connection to an MQTT broker. If Home Assistant is unable to load and setup the MQTT component, it will not setup the MQTT sensor component.

DEPENDENCIES = ['mqtt']

Requirements

Requirements are Python libraries or modules that you would normally install using pip for your component. Home Assistant will try to install the requirements into the deps subdirectory of the Home Assistant configuration directory if you are not using a venv or in something like path/to/venv/lib/python3.6/site-packages if you running in a virtual environment. This will make sure that all requirements are present at startup. If steps fails like missing packages for the compilation of a module or other install errors, the component will fail to load.

Requirements is a list of strings. Each entry is a pip compatible string. For example, the media player Cast platform depends on the Python package PyChromecast v0.6.12:

REQUIREMENTS = ['pychromecast==0.6.12']

Note

Be aware that actual python imports of these dependencies should be done inside functions that use them. This is because Home Assistant installs requirements on demand and so the requirement won't be loaded the first time your component is loaded.

Example:

REQUIREMENTS = ['pychromecast==0.6.12']

def setup(hass, config):
    import pychromecast
    
    <your code goes here>

Custom requirements during development & testing

During development of a component, it can be useful to test against different versions of a requirement. This can be done in two steps, using pychromecast as an example:

• pip install pychromecast==0.6.13 --target ~/.homeassistant/deps
• hass --skip-pip

This will use the specified version, and prevent Home Assistant from trying to override it with what is currently in REQUIREMENTS.

If you need to make changes to a requirement to support your component, it's also possible to pip install from a checkout of the requirement.

• git clone https://github.com/balloob/pychromecast.git
• pip install ./pychromecast
• hass --skip-pip

For testing and development purposes you can also to point to a hosted package in the form of an archive (zip/tar.gz) file as a requirement. GitHub provides archive files for a specific branch, release or even a specific commit. To do that the string in REQUIREMENTS needs to be composed of two parts:

• an URL pointing to the archive file (e.g. https://github.com/my/repo/archive/branch-x.zip)
• a hashtag and pip string (as described above) to declare what package and version that archive file contains

Note: Components and platforms included in Home Assistant should point to published PyPI packages. This ensures that the unit tests will not be slowed down as they can be cached.

For example, the Neato robot vacuum components specifies the v.0.0.5 release on GitHub as a requirement that gets installed as pybotvac version 0.0.5 (pybotvac==0.0.5).

REQUIREMENTS = ['https://github.com/jabesq/pybotvac/archive/v0.0.5.zip#pybotvac==0.0.5']