Config API

class lymph.config.ConfigView(config, prefix)

A ConfigView allows access to a subtree of a Configuration object. It implements the mapping protocol. Dotted path keys are translated into nested dictionary lookups, i.e. cv.get('a.b') is (roughly) equivalent to cv.get('a').get('b').

If a value returned by ConfigView methods is a dict, it will be wrapped in a ConfigView itself. This – and getting dicts from a Configuration object – are the preferred way to create new ConfigViews.


A reference to the root Configuration instance.

class lymph.config.Configuration(values=None)
Parameters:values – an optional initial mapping

Configuration implements the same interface as ConfigView in addition to the methods described here.

load(file, sections=None)

Reads yaml configuration from a file-like object. If sections is not None, only the keys given are imported

load_file(path, sections=None)

Reads yaml configuration from the file at path.

get_raw(key, default)

Like get(), but doesn’t wrap dict values in ConfigView.

create_instance(key, default_class=None, **kwargs)
  • key – dotted config path (e.g. "container.rpc")
  • default_class – class object or fully qualified name of a class
  • kwargs – extra keyword arguments to be passed to the factory

Creates an object from the config dict at key. The instance is created by a factory that is specified by its fully qualified name in a class key of the config dict.

If the factory has a from_config() method it is called with a ConfigView of key. Otherwise, the factory is called directly with the config values as keyword arguments.

Extra keyword arguments to create_instance() are passed through to from_config() or mixed into the arguments if the factory is a plain callable.

If the config doesn’t have a class key the instance is create by default_class, which can be either a fully qualifed name or a factory object.

Given the following config file

    class: pack.age:SomeClass
    extra_arg: 42

you can create an instance of SomeClass

# in pack/
class SomeClass(object):
    def from_config(cls, config, **kwargs):
        assert config['extra_arg'] == 42
        assert kwargs['bar'] is True
        return cls(...)

# in any module
config = Configuration()
config.create_instance('foo', bar=True)
get_instance(key, default_class, **kwargs)

Like create_instance(), but only creates a single instance for each key.