models.py

from flask import json
from sqlalchemy import create_engine, ForeignKey, Enum
from sqlalchemy.orm import scoped_session, sessionmaker, relationship, backref
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column, Integer, String
from sqlalchemy.types import Date


engine = create_engine('mysql://uTrade:m@localhost:8889/uTrade', echo=True)
db_session = scoped_session(sessionmaker(autocommit=False,
                                         autoflush=False,
                                         bind=engine))
Base = declarative_base()
Base.query = db_session.query_property()


def to_json(inst, cls):
    """
    Jsonify the sql alchemy query result.
    """
    convert = dict()
    # add your coversions for things like datetime's
    # and what-not that aren't serializable.
    d = dict()
    for c in cls.__table__.columns:
        v = getattr(inst, c.name)
        if c.type in convert.keys() and v is not None:
            try:
                d[c.name] = convert[c.type](v)
            except:
                d[c.name] = "Error:  Failed to covert using ", str(convert[c.type])
        elif v is None:
            d[c.name] = str()
        else:
            d[c.name] = v
    return json.dumps(d)


# Set your classes here.

class Item(Base):
    __tablename__ = 'Items'

    id = Column(Integer, primary_key=True)
    title = Column(String(150))
    img_url = Column(String(200))
    isbn = Column(String(150))
    authors = Column(String(100))
    edition = Column(Integer)

    def __init__(self, isbn=None, title=None, img_url=None,
                 authors=None, edition=None):
        self.title = title
        self.img_url = img_url
        self.isbn = isbn
        self.authors = authors
        self.edition = edition


    @property
    def json(self):
        return to_json(self, self.__class__)


class Post(Base):
    __tablename__ = 'Posts'

    id = Column(Integer, primary_key=True)
    description = Column(String(240))
    type = Column(Enum('SellerPost', 'RequestPost'))
    price = Column(Integer)  # seller
    book_condition = Column(Enum('New', 'Like New', 'Good', 'Fair', 'Bad'))  # seller
    condition_description = Column(String(250))  # seller
    user_id = Column(Integer, ForeignKey('Users.id'))
    item_id = Column(Integer, ForeignKey('Items.id'))
    item = relationship(Item, backref=backref("item", uselist=False))

    def __init__(self, item_id, description=None, user_id=None,
                 type=None, price=None, book_condition=None, condition_description=None):
        self.description = description
        self.item_id = item_id
        self.user_id = user_id
        self.type = type
        self.price = price
        self.book_condition = book_condition
        self.condition_description = condition_description


class User(Base):
    __tablename__ = 'Users'

    id = Column(Integer, primary_key=True)
    name = Column(String(120), unique=True)
    email = Column(String(120), unique=True)
    posts = relationship(Post, backref='author', lazy='dynamic')
    phone = Column(String(100))


    def __init__(self, name=None, email=None, phone=None):
        self.name = name
        self.email = email
        self.phone = phone

# Create tables.
Base.metadata.create_all(bind=engine)