title: SQLAlchemy (declarative) not creating db or tables
body: <p>I am trying to use postgreSQL with SQLAlchemy. I having some issues because I am a new to SQLAlchemy, and may have misunderstood the documentation. </p>
  
  <p>When I follow the documentation with SQLite I have no problems creating the database and the relations from the classes I specify. However, when I try to do it with Postgre I can't generate the relations or the db, instead I have to create the schemas and the tables manually in the shell.</p>
  
  <p>This is what I currently have:</p>
  
  <pre><code>postgres_url = 'postgresql+psycopg2://some_user:some_password@localhost:5432/testdb'
  
  engine = create_engine(postgres_url)
  
  DB_session = sessionmaker(bind=engine)
  db_session = DB_session()
  
  Base = declarative_base()
  
  Base.metadata.create_all(bind=engine)
  
  #-----------------------------------------------------------
  #                       User Entity
  #-----------------------------------------------------------
  
  
  class User(Base):
  
      __tablename__ = 'users'
      id = Column(Integer, primary_key=True)
      fname = Column(String(45))
      lname = Column(String(45))
      token = Column(String(45))
  
      def __init__(self, fname, lname, token):
          self.fname = fname
          self.lname = lname
          self.token = token
  
      def __repr__(self):
          return 'Token: %s' % self.token
  </code></pre>
  
  <p>When I run the above code after manually creating the db I get a <code>relation "users" does not exist</code>, however, if I create the schema manually everything runs ok. I would appreciate a push in the right direction.</p>