Cfg-Loader

Cfg-Loader is a library that allows to easily load configuration settings. It uses marshmallow to deserialize input data into a target format configuration data.

Main features

• input data validation and automatic processing using marshmallow
• substitution of environment variables in input data (following docker compose variable substitution syntax)
• configuration loading from .yaml file

Requirements

• Python>=3.5

A simple example

>>> from cfg_loader import ConfigSchema, BaseConfigLoader
>>> from marshmallow import fields

# Declare your configuration schema
>>> class MyConfigSchema(ConfigSchema):
...     setting1 = fields.Str()
...     setting2 = fields.Int(required=True)
...     setting3 = fields.Float(missing=13.2)

# Declare mapping to substitute environment variable
>>> substitution_mapping = {'FILE_PATH': 'file'}

# Initialize config loader
>>> my_config_loader = BaseConfigLoader(MyConfigSchema, substitution_mapping=substitution_mapping)

# Load configuration
>>> config = my_config_loader.load({'setting1': '/home/folder/${FILE_PATH?:file path required}', 'setting2': '4'})
>>> config == {'setting1': '/home/folder/file', 'setting2': 4, 'setting3': 13.2}
True

# Invalid input data
>>> my_config_loader.load({'setting1': '/home/folder/${FILE_PATH?:file path required}', 'setting3': 13.4})
Traceback (most recent call last):
...
cfg_loader.exceptions.ValidationError: {'setting2': ['Missing data for required field.']}

>>> my_config_loader.load({'setting2': 12, 'setting3': 'string'})
Traceback (most recent call last):
...
cfg_loader.exceptions.ValidationError: {'setting3': ['Not a valid number.']}

# Variable substitution invalid
>>> my_config_loader.load({'setting2': '${UNSET_VARIABLE?Variable "UNSET_VARIABLE" required}'})
Traceback (most recent call last):
...
cfg_loader.exceptions.UnsetRequiredSubstitution: Variable "UNSET_VARIABLE" required

Documentation

Full documentation is available at https://cfg-loader.readthedocs.io/en/stable/.