sqlalchemy-orm-relationship.markdown

title: sqlalchemy.orm relationship Example Code category: page slug: sqlalchemy-orm-relationship-examples sortorder: 500031072 toc: False sidebartitle: sqlalchemy.orm relationship meta: Python example code that shows how to use the relationship callable from the sqlalchemy.orm module of the SQLAlchemy project.

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

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

Example 1 from graphene-sqlalchemy

graphene-sqlalchemy (project documentation and PyPI package information) is a SQLAlchemy integration for Graphene, which makes it easier to build GraphQL-based APIs into Python web applications. The package allows you to subclass SQLAlchemy classes and build queries around them with custom code to match the backend queries with the GraphQL-based request queries. The project is provided as open source under the MIT license.

graphene-sqlalchemy / graphene_sqlalchemy / tests / models.py

# models.py
from __future__ import absolute_import

import enum

from sqlalchemy import (Column, Date, Enum, ForeignKey, Integer, String, Table,
                        func, select)
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.hybrid import hybrid_property
~~from sqlalchemy.orm import column_property, composite, mapper, relationship

PetKind = Enum("cat", "dog", name="pet_kind")


class HairKind(enum.Enum):
    LONG = 'long'
    SHORT = 'short'


Base = declarative_base()

association_table = Table(
    "association",
    Base.metadata,
    Column("pet_id", Integer, ForeignKey("pets.id")),
    Column("reporter_id", Integer, ForeignKey("reporters.id")),
)


class Editor(Base):
    __tablename__ = "editors"
    editor_id = Column(Integer(), primary_key=True)
    name = Column(String(100))



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


    pet_kind = Column(PetKind, nullable=False)
    hair_kind = Column(Enum(HairKind, name="hair_kind"), nullable=False)
    reporter_id = Column(Integer(), ForeignKey("reporters.id"))


class CompositeFullName(object):
    def __init__(self, first_name, last_name):
        self.first_name = first_name
        self.last_name = last_name

    def __composite_values__(self):
        return self.first_name, self.last_name

    def __repr__(self):
        return "{} {}".format(self.first_name, self.last_name)


class Reporter(Base):
    __tablename__ = "reporters"

    id = Column(Integer(), primary_key=True)
    first_name = Column(String(30), doc="First name")
    last_name = Column(String(30), doc="Last name")
    email = Column(String(), doc="Email")
    favorite_pet_kind = Column(PetKind)
~~    pets = relationship("Pet", secondary=association_table, backref="reporters", order_by="Pet.id")
~~    articles = relationship("Article", backref="reporter")
~~    favorite_article = relationship("Article", uselist=False)

    @hybrid_property
    def hybrid_prop(self):
        return self.first_name

    column_prop = column_property(
        select([func.cast(func.count(id), Integer)]), doc="Column property"
    )

    composite_prop = composite(CompositeFullName, first_name, last_name, doc="Composite")


class Article(Base):
    __tablename__ = "articles"
    id = Column(Integer(), primary_key=True)
    headline = Column(String(100))
    pub_date = Column(Date())
    reporter_id = Column(Integer(), ForeignKey("reporters.id"))


class ReflectedEditor(type):

    @classmethod
    def __subclasses__(cls):


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

Example 2 from sqlalchemy-datatables

sqlalchemy-datatables (PyPI package information) is a helper library that makes it easier to use SQLAlchemy with the jQuery JavaScript DataTables plugin. This library is designed to be web framework agnostic and provides code examples for both Flask and Pyramid.

The project is built and maintained by Michel Nemnom (Pegase745) and is open sourced under the MIT license.

sqlalchemy-datatables / tests / models.py

# models.py
import datetime

from sqlalchemy import Column, Date, DateTime, ForeignKey, Integer, String, func
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.hybrid import hybrid_property
~~from sqlalchemy.orm import backref, relationship

Base = declarative_base()


class User(Base):

    __tablename__ = 'users'

    id = Column(Integer, primary_key=True)
    name = Column(String, unique=True)
    created_at = Column(DateTime, default=datetime.datetime.utcnow)
    birthday = Column(Date)
~~    address = relationship('Address', uselist=False, backref=backref('user'))

    def __unicode__(self):
        return '%s' % self.name

    def __repr__(self):
        return '<%s#%s>' % (self.__class__.__name__, self.id)

    @hybrid_property
    def dummy(self):
        return self.name[0:3]

    @dummy.expression
    def dummy(cls):
        return func.substr(cls.name, 0, 3)


class Address(Base):

    __tablename__ = 'addresses'

    id = Column(Integer, primary_key=True)
    description = Column(String, unique=True)
    user_id = Column(Integer, ForeignKey('users.id'))



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