Python configuration utilities

Implementation of key-value pair based configuration for Python applications.

Features:

• support for most common sources of application settings
• support for overriding settings in sequence
• support for nested structures and lists, using attribute notation
• strategy to use environment specific settings

This library is freely inspired by .NET Core Microsoft.Extensions.Configuration namespace and its pleasant design (ref. MSDN documentation, Microsoft Extensions Configuration Deep Dive).

The main class is influenced by Luciano Ramalho`s example of JSON structure explorer using attribute notation, in his book Fluent Python.

Supported sources:

• yaml files
• json files
• ini files
• environmental variables
• dictionaries
• keys and values

Installation

pip install roconfiguration

Examples

YAML file and environmental variables

In this example, configuration will be comprised of anything inside a file settings.yaml and environmental variables. Settings are applied in order, so environmental variables with matching name override values from the yaml file.

from roconfiguration import Configuration

config = Configuration()

config.add_yaml_file("settings.yaml")

config.add_environmental_variables()

YAML file, optional file by environment

In this example, if an environmental variable with name APP_ENVIRONMENT and value dev exists, and a configuration file with name settings.dev.yaml is present, it is read to override values configured in settings.yaml file.

import os
from roconfiguration import Configuration

environment_name = os.environ["APP_ENVIRONMENT"]

config = Configuration()

config.add_yaml_file("settings.yaml")
config.add_yaml_file(f"settings.{environment_name}.yaml", optional=True)

config.add_environmental_variables()

Filtering environmental variables by prefix

import os
from roconfiguration import Configuration

config = Configuration()

# will read only environmental variables
# starting with "APP_", case insensitively
config.add_environmental_variables("APP_")

Ini files

Ini files are parsed using the built-in configparser module, therefore support [DEFAULT] section; all values are kept as strings.

from roconfiguration import Configuration

config = Configuration()

config.add_ini_file("settings.ini")

JSON files

JSON files are parsed using the built-in json module.

from roconfiguration import Configuration

config = Configuration()

config.add_json_file("settings.json")

Dictionaries

from roconfiguration import Configuration

config = Configuration({"host": "localhost", "port": 8080})

config.add_map({"hello": "world", "example": [{"id": 1}, {"id": 2}]})

assert config.host == "localhost"
assert config.port == 8080
assert config.hello == "world"
assert config.example[0].id == 1
assert config.example[1].id == 2

Keys and values

from roconfiguration import Configuration

config = Configuration({"host": "localhost", "port": 8080})

config.add_value("port", 44555)

assert config.host == "localhost"
assert config.port == 44555

Overriding nested values

config = Configuration(
    {
        "a": {
            "b": 1,
            "c": 2,
            "d": {
                "e": 3,
                "f": 4,
            },
        }
    }
)

assert config.a.b == 1
assert config.a.d.e == 3
assert config.a.d.f == 4

config.add_value("a:d:e", 5)

assert config.a.d.e == 5
assert config.a.d.f == 4

Overriding nested values using env variables

config = Configuration(
    {
        "a": {
            "b": 1,
            "c": 2,
            "d": {
                "e": 3,
                "f": 4,
            },
        }
    }
)

assert config.a.b == 1
assert config.a.d.e == 3
assert config.a.d.f == 4

# NB: if an env variable such as:
# a:d:e=5
# or...
# a__d__e=5
#
# is defined, it overrides the value  from the dictionary

config.add_environmental_variables()

assert config.a.d.e == 5

Overriding values in list items using env variables

config = Configuration(
    {
        "b2c": [
            {"tenant": "1"},
            {"tenant": "2"},
            {"tenant": "3"},
        ]
    }
)

config.add_value("b2c:1:tenant", "4")

assert config.b2c[0].tenant == "1"
assert config.b2c[1].tenant == "4"
assert config.b2c[2].tenant == "3"

Develop and run tests locally

pip install -r requirements.txt

# run tests using automatic discovery:
pytest