Double Underscore Notation

Stdnet makes extensive use of the __ double-underscore notation in several parts of the API.

• A Query with range and text lookups:

  >>> from stdnet import odm
  >>> models = odm.Router()
  >>> models.register(MyModel)
  >>> qs = odm.mymodel.filter(size__gt=40, description__contains='technology')
  

• An Query on a Field of a related model. For example, in the Position model one can filter, exclude or sort, with respect the instrument ccy Field in this way:

  qs = models.position.filter(instrument__ccy='EUR')
  qs = models.position.exclude(instrument__ccy='EUR')
  qs = models.position.query().sort_by('instrument__ccy')
  

• In conjunction with load_only query method when you need to load only a subset of a related model fields:

  qs = models.position.query().load_only('size', 'instrument__ccy')
  

• In the StdModel.get_attr_value() method, for example:

  p.get_attr_value('instrument')
  # same as
  p.instrument
  

  and:

  p.get_attr_value('instrument__ccy')
  # same as
  p.instrument.ccy