resconfig 20.4.0a0

Application resource configuration library for Python

resconfig

resconfig is a minimalistic application configuration library for Python. It is essentially a thin wrapper around nested dicts and can:

• Read from multiple configuration file formats: INI, JSON, TOML, and YAML.

• Dynamically reload configuration at run time: Watch functions can be attached to any keys within the configuration, so that separate resources can be reloaded and managed.

• Access nested configuration item with a .-delimited string key: The underlying configuration data structure is nested dicts, but no need to manually traverse or use the verbose config["foo"]["bar"] form (can use config["foo.bar"] instead).

• Apply schema (experimental): Type casting can be performed upon loading configuration from files.

Installation

$ pip install resconfig

Basic Usage

from resconfig import ResConfig

config = ResConfig()              # create empty config
config.load_from_yaml("pg.yaml")  # load config from YAML file
dbname = config.get("pg.dbname")  # get value at config["pg"]["dbname"]

config = ResConfig({"pg": {"dbname": "foo"}})  # with default config
config = ResConfig({"pg.dbname": "foo"}})      # this also works

Watching for Configuration Changes

The ResConfig object is aware of changes to its configuration. Watch functions can be registered to watch changes happening at any nested key to act on them. For example,

import signal

from resconfig import Action, ResConfig

config = ResConfig(skip_reload_on_init=True)  # do not immediately load config


@config.watch("nested.key")
def act_on_nested_key(action, old, new):
    if action == Action.ADDED:
        # ... do something when the new value is added to nested.key ...
    elif action == Action.MODIFIED:
        # ... do something when the value at nested.key is modified ...
    elif action == Action.RELOADED:
        # ... do something when the value at nested.key is reloaded ...
    elif action == Action.REMOVED:
        # ... do something when the value at nested.key is removed ...


def reload(signum=None, stack_frame=None):
    config.load_from_yaml("myconf.yml")


signal.signal(signal.SIGHUP, reload)  # run reload on receiving SIGHUP signal

reload()  # ready to do the initial config loading

Here, the act_on_nested_key function is invoked whenever an action occurs at the nested.key of the configuration and can decide what to do with the old and/or new values. In this code, the configuration reload function is also a signal handler for SIGHUP and is triggered on the process receiving the signal.

The same watch function above can be registered in a couple more different ways, via the method

config.register("nested.key", act_on_nested_key)

or as an argument to ResConfig

config = ResConfig(watchers={"nested.key": act_on_nested_key})

Development

$ pip install .[dev]
$ pre-commit install

Running Tests

$ python setup.py test

License

Apache License, Version 2.0