alphaconf 0.2.2

Write simple scripts leveraging omegaconf

Alphaconf

A small library to ease writing parameterized scripts. The goal is to execute a single script and be able to overwrite the parameters easily. The configuration is based on omegaconf.

To run multiple related tasks, there is an integration with invoke. If you need something more complex, like running multiple instances of the script, take a look at hydra-core or use another script to launch multiple instances.

Demo and application

DEMO

To run an application, you need...

import alphaconf
# each module or application can declare the default configuration they need
# it will always be loaded before application startup
alphaconf.setup_configuration("""
server:
  url: http://default
  user: ${oc.env:USER}
""")

def main():
    log = logging.getLogger()
    # get the DictConfig from the current application
    log.info('app name:', alphaconf.configuration().application.name)
    # shortcut to get an option as a dict, str, etc.
    log.info('server.user:', alphaconf.get('server.user'))
    log.info('has server.user:', alphaconf.get('server.user', bool))

if __name__ == '__main__':
    # run the application
    alphaconf.Application(
        name='example',
        version='0.1',
    ).run(main)

Secrets

When showing the configuration, by default configuration keys which are secrets, keys or passwords will be masked. Another good practice is to have a file containing the password which you can retrieve using alphaconf.get('secret_file', 'read_strip').

Invoke integration

Just add the lines below to parameterize invoke. Note that the argument parsing to overwrite configuration will work only when the script is directly called.

ns = Collection()  # define the invoke configuration
import alphaconf.invoke
alphaconf.setup_configuration({'backup': 'all'})
alphaconf.invoke.invoke_application(__name__, ns)

How the configuration is loaded

When running a program, first dotenv is used to load environment variables from a .env file - this is optional.

Then configuration is built from:

• default configurations defined using (alphaconf.setup_configuration)
• application key is generated
• configuration files from the system (from your HOME and configuration directories)
• environment variables based on key prefixes, except "BASE" and "PYTHON"; if you have a configuration key "abc", all environment variables starting with "ABC_" will be loaded where keys are converted to lower case and "_" to ".": "ABC_HELLO=a" would set "abc.hello=a"
• key-values from the program arguments

Finally, the configuration is fully resolved once and logging is configured.

Configuration templates and resolvers

Omegaconf's resolvers may be used as configuration values. For example, ${oc.env:USER,me} would resolve to the environment variable USER with a default value "me". Similarly, ${oc.select:path} will resolve to another configuration value.

The select is used to build multiple templates for configurations by providing base configurations. An argument --select key=template is a shortcut for key=${oc.select:base.key.template}. So, logging: ${oc.select:base.logging.default} resolves to the configuration dict defined in base.logging.default and you can select it using --select logging=default.