SQLAlchemy Model Example Code

SQLAlchemy (source code) is a Python library for accessing persistent data stored in relational databases either through raw SQL or an object-relational mapper.

Example 1 from flask-website

flask-website is the code that runs the Flask official project website. Yes, Flask is used to create and run the Flask project website. Did you expect the creators of Flask to use Django instead?

flask-website / flask_website / database.py

from datetime import datetime
from sqlalchemy import create_engine, Column, Integer, String, DateTime, \
     ForeignKey, event
from sqlalchemy.orm import scoped_session, sessionmaker, backref, relation
from sqlalchemy.ext.declarative import declarative_base

from werkzeug import cached_property, http_date

from flask import url_for, Markup
from flask_website import app, search

engine = create_engine(app.config['DATABASE_URI'],
db_session = scoped_session(sessionmaker(autocommit=False,

def init_db():

Model = declarative_base(name='Model')
Model.query = db_session.query_property()

class User(Model):
    __tablename__ = 'users'
    id = Column('user_id', Integer, primary_key=True)
    openid = Column('openid', String(200))
    name = Column(String(200))

    def __init__(self, name, openid):
        self.name = name
        self.openid = openid

    def to_json(self):
        return dict(name=self.name, is_admin=self.is_admin)

    def is_admin(self):
        return self.openid in app.config['ADMINS']

    def __eq__(self, other):
        return type(self) is type(other) and self.id == other.id

    def __ne__(self, other):
        return not self.__eq__(other)

class Category(Model):
    __tablename__ = 'categories'
    id = Column('category_id', Integer, primary_key=True)
    name = Column(String(50))
    slug = Column(String(50))

    def __init__(self, name):
        self.name = name
        self.slug = '-'.join(name.split()).lower()

    def to_json(self):
        return dict(name=self.name, slug=self.slug, count=self.count)

    def count(self):
        return self.snippets.count()

    def url(self):
        return url_for('snippets.category', slug=self.slug)

class Snippet(Model, search.Indexable):
    __tablename__ = 'snippets'
    id = Column('snippet_id', Integer, primary_key=True)
    author_id = Column(Integer, ForeignKey('users.user_id'))
    category_id = Column(Integer, ForeignKey('categories.category_id'))
    title = Column(String(200))
    body = Column(String)
    pub_date = Column(DateTime)

    author = relation(User, backref=backref('snippets', lazy='dynamic'))
    category = relation(Category, backref=backref('snippets', lazy='dynamic'))

    search_document_kind = 'snippet'

    def __init__(self, author, title, body, category):
        self.author = author
        self.title = title
        self.body = body
        self.category = category
        self.pub_date = datetime.utcnow()

    def to_json(self):
        return dict(id=self.id, title=self.title,
                    comments=[c.to_json() for c in self.comments],

    def get_search_document(self):
        return dict(

    def describe_search_result(cls, result):
        obj = cls.query.get(int(result['id']))
        if obj is not None:
            text = obj.rendered_body.striptags()
            return Markup(result.highlights('content', text=text)) or None

    def url(self):
        return url_for('snippets.show', id=self.id)

    def rendered_body(self):
        from flask_website.utils import format_creole
        return format_creole(self.body)

class Comment(Model):
    __tablename__ = 'comments'
    id = Column('comment_id', Integer, primary_key=True)
    snippet_id = Column(Integer, ForeignKey('snippets.snippet_id'))
    author_id = Column(Integer, ForeignKey('users.user_id'))
    title = Column(String(200))
    text = Column(String)
    pub_date = Column(DateTime)

    snippet = relation(Snippet, backref=backref('comments', lazy=True))
    author = relation(User, backref=backref('comments', lazy='dynamic'))

    def __init__(self, snippet, author, title, text):
        self.snippet = snippet
        self.author = author
        self.title = title
        self.text = text
        self.pub_date = datetime.utcnow()

    def to_json(self):
        return dict(author=self.author.to_json(),

    def rendered_text(self):
        from flask_website.utils import format_creole
        return format_creole(self.text)

class OpenIDAssociation(Model):
    __tablename__ = 'openid_associations'
    id = Column('association_id', Integer, primary_key=True)
    server_url = Column(String(1024))
    handle = Column(String(255))
    secret = Column(String(255))
    issued = Column(Integer)
    lifetime = Column(Integer)
    assoc_type = Column(String(64))

class OpenIDUserNonce(Model):
    __tablename__ = 'openid_user_nonces'
    id = Column('user_nonce_id', Integer, primary_key=True)
    server_url = Column(String(1024))
    timestamp = Column(Integer)
    salt = Column(String(40))

event.listen(db_session, 'after_flush', search.update_model_based_indexes)
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