Sqlalchemy foreignkey and many to many field joining

sqlalchemy_foreignkey_and_many_to_many_fied_join.py

# pre rehnquist:
# >psycopg2
# >python version 3.*
#> SQLAlchemy
#
# Outcome:
# >using Sqlalchemy create table and call data from database
# >Table sync in postgresql

from sqlalchemy import (
    Table,
    Column,
    Index,
    Integer,
    Text,
    String,
    DateTime,
    Date,
    ForeignKey,
    create_engine,
    desc,
    asc,
    Boolean,
    and_
)
from sqlalchemy.orm import load_only
from sqlalchemy.orm import relationship, backref
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.engine.url import URL
import datetime
from sqlalchemy.orm import sessionmaker

DeclarativeBase = declarative_base()

DATABASE = {
    'drivername': 'postgres',
    'host': '127.0.0.1',
    'port': '5432',
    'username': 'admin',
    'password': '789',
    'database': 'tesdb'
}


def db_connect():
    """
    Performs database connection using database settings from settings.py.
    Returns sqlalchemy engine instance
    """
    return create_engine(URL(**DATABASE))


def create_deals_table(engine):
    """"""
    DeclarativeBase.metadata.create_all(engine)


def db_session():
    engine = db_connect()
    Session = sessionmaker(bind=engine)
    session = Session()
    return session

DBSession = db_session()



tags = Table('tag_task', DeclarativeBase.metadata,
    Column('task_id', Integer, ForeignKey('task.id')),
    Column('tag_id', Integer, ForeignKey('tags.id'))
)


class Task(DeclarativeBase):
    __tablename__ = 'task'

    id = Column(Integer, primary_key=True)
    task_project_type = Column(Text)
    task_title = Column(Text)
    task_detail = Column(Text)
    task_created_by = Column(Text)
    task_updated_by = Column(Text)
    task_assign_to = Column(Text)
    task_created_on = Column(DateTime, default=datetime.datetime.now())
    task_updated_on = Column(DateTime)
    task_deadline = Column(Date)
    task_tags_list = Column(Text)
    task_status = Column(Boolean, default=False)
    task_tags = relationship('Tag', secondary=tags, backref = backref('task', lazy='dynamic'))
    comments = relationship('Comment', backref='task', lazy='dynamic')

class Tag(DeclarativeBase):
    __tablename__ = 'tags'

    id = Column(Integer, primary_key=True)
    name = Column(Text, unique=True, nullable=False)

class Comment(DeclarativeBase):

    __tablename__ = 'comments'

    id = Column(Integer, primary_key=True)
    comment_description = Column(Text)
    comment_created_by = Column(Text)
    comment_created_on = Column(DateTime, default=datetime.datetime.now())
    comment_updated_on = Column(DateTime)
    task_id    =   Column(Integer, ForeignKey('task.id'))

if __name__ == '__main__':
    engine = db_connect()
    create_deals_table(engine)