Aegir

Aegir is a library allowing you to add configuration options to your Python project without any additional work.

Usage

This system articulates around configuration entries, being class that have attributes that can be automatically overridden by a configuration file.

Here is an example of a configuration entry:

# file: my_app/example.py
from aegir import ConfigEntry

class MyEntry(ConfigEntry):
    my_str: str = "default_value"
    my_int: int = 42

You are able to access those attributes normally:

>>> from my_app.example import MyEntry
>>> MyEntry.my_str
"default_value"
>>> MyEntry.my_int
42

You are now also able to load a configuration file, using the load() function. This function will override entries based on the dotted path to the module of the entry.

Using the example above, the configuration file could look like:

# file: my_config.yaml
my_app.example:
  my_str: "new_value"

The load() function will replace those attributes with the ones from the configuration file.

>>> from aegir import load
>>> load("my_config.yaml")
>>> from my_app.example import MyEntry
>>> MyEntry.my_str
"new_value"

Changing the default path

If you do not wish to use the module path, but rather a custom one, you can use the path metaclass argument when creating your instance.

class MyEntry(ConfigEntry, path="custom.path"):
    ...

The entry will now be treated as if it was in the custom.path module.

Default arguments

It is possible to not provide default arguements to your configuration entry.

class MyEntry(ConfigEntry):
    without_default: str

If the configuration file does not contain the attribute, the ConfigurationKeyError exception will be raised. This is useful if you want to make sure that a configuration entry is always present.

Bear in mind that the configuration file must be loaded before the module containing the entry is created. You can bypass that restriction using the check_attributes metaclass argument, such as:

class MyEntry(ConfigEntry, check_attributes=False):
    without_default: str

If you wish, you are still able to call check_attributes() manually later on to trigger that check.

!REF constructors

You can use this constructor inside your configuration file to reference another attributes:

my_app.example:
  my_str: !REF my_other_entry.my_str

API documentation

For more details about the API, and some other interfaces not listed in this document, please see the full documentation.

Installation

The package is available on PyPI under the name aegir.

$ pip install aegir
$ poetry add aegir
$ pipenv install aegir

Contributing

If you would like to join, please join our Discord server and introduce yourself in #aegir. Thank you for your interest in our project!