py-entity

Basic Python Entities

An entity is useful for preparing models for an API or view.

Allows view or API UI specific logic to be removed from models.

Example

We have some object..

class GeorgeWashington(object):
    id = 1776
    first_name = 'George'
    last_name = 'Washington'
    phone_number = '(202) 456-1111'
    phone_number_private = True
    email = 'prez1@whouse.gov'
    accomplishments = ['president', 'general', 'quarter model', 'woodworking']
    birthday = datetime.datetime(1732, 2, 22, 0, 0)

Converting this object to json would take a bit of work. We need to write some kind of to_dictionary method, or a custom encoder. There will stil probably be an issue with the datetime (not JSON-encodable) as well as the fact that we want to conditionally include the phone_number, as long as phone_number_private is not True.

Using an Entity:

class UserEntity(pyentity.Entity):
    _FIELDS_ = [
        'id',
        'name',
        'phone_number',
        'email',
        'accomplishments',
        'birthday',
    ]
    _ALIAS_ = 'user'

    def name(self):
        return "%s %s" % (self.user.first_name, self.user.last_name)

    def birthday(self):
        return self.user.birthday.isoformat()

    def phone_number(self):
        if self.user.phone_number_private:
            raise pyentity.SuppressField
        return self.user.phone_number

Then,

george_entity = UserEntity(GeorgeWashington())
print json.dumps(george_entity(), indent=2)

{
  "email": "prez1@whouse.gov", 
  "accomplishments": [
    "president", 
    "general", 
    "quarter model", 
    "woodworking"
  ], 
  "id": 1776, 
  "birthday": "1732-02-22T00:00:00", 
  "name": "George Washington"
}

Somtimes, we want to have different views over the same data. One may be a detailed description of an object, but some other may just be a summary. Entity inheritance helps here.

class SummaryEntity(UserEntity):
    _FIELDS_ = ['name', 'email']

Then,

summary_entity = SummaryEntity(GeorgeWashington())
print json.dumps(summary_entity(), indent=2)

{
  "name": "George Washington", 
  "email": "prez1@whouse.gov"
}