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Configuration manager for cloud native application, support configuration stored in memory, in files, in databases

Project description

Latest version on Supported Python versions Travis Pipelines build status codecov


Config42 is a complete configuration reader and manager. It aims to read the configuration from different sources: a memory Dict object, an external file ( YAML, JSON, INI, PYTHON Object ), an SQL database (Postgres, MySQL, Oracle) alternatively, Key-value data store ( Etcd )

It is designed to be extensible. Different handlers could support another data store. All PR are welcome.

Related blog posts


From sources: (Bleeding edge)

pip install git+

From PyPi: (Stable)

pip install config42

Getting started

Config42 abstract loading configuration complexity. Let config42 manage your configuration for you.

Using environment variables

Most of the containerised applications change behaviour from environment variables to change their behaviour. config42 handle it easily.

Here a working sample examples/docker

from config42 import ConfigManager
env_config = ConfigManager(prefix="MYAPP")
# Access to configuration via the ConfigManager getter
print("username : {}".format(env_config.get('username')))
print("nested key  : {}".format(env_config.get('')))

Export variables to system environment

export MYAPP_USERNAME=yuri
export MYAPP_SECRET_ONE=password

Export variables to process environment

MYAPP_USERNAME=yuri2 python

Once you build you docker image, you may run the application by export variables into the container environment

docker run  -e MYAPP_USERNAME=yuri -e MYAPP_SECRET_ONE=secret testconfig42:latest

Using Etcd Handler

To load configuration from Etcd data store, you need to specify the keyspace where the configuration is located, Etcd host(s) and port(s).

from config42 import ConfigManager
from config42.handlers import Etcd

config = ConfigManager(handler=Etcd, keyspace='/config')
# config = ConfigManager(handler=Etcd, keyspace='/config', port=4001)
# config = ConfigManager(handler=Etcd, keyspace='/config', host='', port=4001)
# config = ConfigManager(handler=Etcd, keyspace='/config', host=(('', 4001), ('', 4002), ('', 4003)))

Note : Etcd handler use python-etcd client All args after keyspace are passed to Etcd.Client class.

Using Filehandler, Load configuration from file

from pprint import pprint
from config42 import ConfigManager
from config42.handlers import FileHandler

# Yaml files
config = ConfigManager(handler=FileHandler, path='files/config1.yml')
#config = ConfigManager(handler=FileHandler, path='files/config1.yaml')

# Json file 
#config = ConfigManager(handler=FileHandler, path='files/config1.json')

#INI structure support only one level of nesting (Sections = { key: value }) 
#config = ConfigManager(handler=FileHandler, path='files/config.ini')

CONFIG = config.as_dict()

print("Configuration has been loaded")

# Access to configuration via the ConfigManager getter
print("application_name : {}".format(config.get('application_name')))
print("nested key : {}".format(config.get('nested.nestedkey.key2')))

# Access to configuration via the as dict utility; it will dump configuration file to data store if updated
print("user : {}".format(config.as_dict()['user']))

# Access to configuration via the classic CONFIG global variable
print("application_name : {}".format(CONFIG['application_name']))
print("nested key : {}".format(CONFIG['nested']['nestedkey']['key2']))

Using argparse, Load configuration from commandline parameters (sys.argv)

from config42 import ConfigManager
from config42.handlers.argparse import Argparse

schema = [
    dict(key="user", description="username"),
    dict(key="verbosity", description="verbosity level", choices=["debug", "info"]),

config = ConfigManager(handler=Argparse, schema=schema)

Please take a look to the example using Argparse's handler

Real use case

Below is a real use from Instabot-Py project that uses this library as a configuration manager.

config42 handles 4 sources of configuration data in order of priority:

  • Default configuration from Dict Object
  • Environment variables prefixed by INSTABOT
  • Local file where value located in config.file (INSTABOT_CONFIG_FILE)
  • Etcd data-store

ref :

import logging.config
import os

from config42 import ConfigManager

from instabot_py.default_config import DEFAULT_CONFIG

env_config = ConfigManager(prefix="INSTABOT")
logging.basicConfig(level=logging.DEBUG if env_config.get("debug") else logging.INFO)
LOGGER = logging.getLogger(__name__)
config = ConfigManager()

config_file = config.get("config.file")
config_etcd = config.get("config.etcd")

if config_file:
    if config_file.startswith("/"):
        config_path = config_file
        cwd = os.getcwd()
        config_path = cwd + "/" + config_file
    config.set_many(ConfigManager(path=config_path.replace('//', '/')).as_dict())"Setting configuration from {} : OK".format(config_file))

if config_etcd:
    if not config_etcd.get("keyspace"):
        raise Exception("etcd Keyspace is mandatory")
            "Setting external configuration from {} : OK".format(config_file))
    except Exception as exc:
            "Setting external configuration from ({}) : NOT OK".format(
                ",".join({key + "=" + value for key, value in config_etcd.items() or {}})

        raise exc



Yaml configuration files

pip install Pyaml

Etcd data store

pip install python-etcd


The following packages are needed to run tests and coverage

pip install tox pytest-cov pytest flake8


pip install -r requirements/ci.txt
pip install -r requirements/tests.txt

Usage examples


  • readthedoc with sphinx



  • Add set default variables feature


  • Add Environment Handler


  • Add Etcd Handler
  • Add Ini Yaml, Json Handlers

Project details

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