from sqlalchemy import create_engine, MetaData
from sqlalchemy.orm import sessionmaker
from sqlalchemy.ext.declarative import declarative_base

username = "username"
password = "password"
host = "localhost"
database = "dbname"

engine = create_engine("mysql://{}:{}@{}/{}".format(username, password, host, database))
Base = declarative_base(engine)

def loadSession():
    metadata = Base.metadata
    Session = sessionmaker(bind=engine)
    session = Session()
    return session

class Company(Base):
    __tablename__ = 'company'
    __table_args__ = {'autoload': True}

session = loadSession()
print session.query(Company).first()