sqlalchemy-orm-attributes.markdown

title: sqlalchemy.orm attributes Example Code category: page slug: sqlalchemy-orm-attributes-examples sortorder: 500031062 toc: False sidebartitle: sqlalchemy.orm attributes meta: Python example code that shows how to use the attributes callable from the sqlalchemy.orm module of the SQLAlchemy project.

attributes is a callable within the sqlalchemy.orm module of the SQLAlchemy project.

ColumnProperty, CompositeProperty, Load, Mapper, Query, RelationshipProperty, Session, SynonymProperty, aliased, backref, class_mapper, column_property, composite, interfaces, mapper, mapperlib, object_mapper, object_session, query, relationship, session, sessionmaker, and strategies are several other callables with code examples from the same sqlalchemy.orm package.

Example 1 from sqlalchemy-utils

sqlalchemy-utils (project documentation and PyPI package information) is a code library with various helper functions and new data types that make it easier to use SQLAlchemy when building projects that involve more specific storage requirements such as currency. The wide array of data types includes ranged values and aggregated attributes.

sqlalchemy-utils / sqlalchemy_utils / generic.py

# generic.py
from collections.abc import Iterable

import six
import sqlalchemy as sa
from sqlalchemy.ext.hybrid import hybrid_property
~~from sqlalchemy.orm import attributes, class_mapper, ColumnProperty
from sqlalchemy.orm.interfaces import MapperProperty, PropComparator
from sqlalchemy.orm.session import _state_session
from sqlalchemy.util import set_creation_order

from .exceptions import ImproperlyConfigured
from .functions import identity


class GenericAttributeImpl(attributes.ScalarAttributeImpl):
~~    def get(self, state, dict_, passive=attributes.PASSIVE_OFF):
        if self.key in dict_:
            return dict_[self.key]

        session = _state_session(state)
        if session is None:
            return None

        discriminator = self.get_state_discriminator(state)
        target_class = state.class_._decl_class_registry.get(discriminator)

        if target_class is None:
            return None

        id = self.get_state_id(state)


## ... source file abbreviated to get to attributes examples ...


            self.property = prop
            self._parententity = parentmapper

        def __eq__(self, other):
            discriminator = six.text_type(type(other).__name__)
            q = self.property._discriminator_col == discriminator
            other_id = identity(other)
            for index, id in enumerate(self.property._id_cols):
                q &= id == other_id[index]
            return q

        def __ne__(self, other):
            return -(self == other)

        def is_type(self, other):
            mapper = sa.inspect(other)
            class_names = [six.text_type(other.__name__)]
            class_names.extend([
                six.text_type(submapper.class_.__name__)
                for submapper in mapper._inheriting_mappers
            ])

            return self.property._discriminator_col.in_(class_names)

    def instrument_class(self, mapper):
~~        attributes.register_attribute(
            mapper.class_,
            self.key,
            comparator=self.Comparator(self, mapper),
            parententity=mapper,
            doc=self.doc,
            impl_class=GenericAttributeImpl,
            parent_token=self
        )


def generic_relationship(*args, **kwargs):
    return GenericRelationshipProperty(*args, **kwargs)


        target = session.query(target_class).get(id)

        return target

    def get_state_discriminator(self, state):
        discriminator = self.parent_token.discriminator
        if isinstance(discriminator, hybrid_property):
            return getattr(state.obj(), discriminator.__name__)
        else:
            return state.attrs[discriminator.key].value

    def get_state_id(self, state):
        return tuple(state.attrs[id.key].value for id in self.parent_token.id)

    def set(self, state, dict_, initiator,
~~            passive=attributes.PASSIVE_OFF,
            check_old=None,
            pop=False):

        dict_[self.key] = initiator

        if initiator is None:
            for id in self.parent_token.id:
                dict_[id.key] = None
            dict_[self.parent_token.discriminator.key] = None
        else:
            class_ = type(initiator)
            mapper = class_mapper(class_)

            pk = mapper.identity_key_from_instance(initiator)[1]

            discriminator = six.text_type(class_.__name__)

            for index, id in enumerate(self.parent_token.id):
                dict_[id.key] = pk[index]
            dict_[self.parent_token.discriminator.key] = discriminator


class GenericRelationshipProperty(MapperProperty):



## ... source file continues with no further attributes examples...