updated imports and datetime

diner.py

 from sqlalchemy import create_engine, Column, Integer, String, DateTime, ForeignKey
-from sqlalchemy.ext.declarative import declarative_base
-from sqlalchemy.orm import sessionmaker, relationship
+from sqlalchemy.orm import declarative_base, sessionmaker, relationship
 
 
 # In Python, unlike many languages, it is possible to create new classes at
@@ -8,13 +7,14 @@ from sqlalchemy.orm import sessionmaker, relationship
 # class that we can use for objects that we want SQLAlchemy to persist in a
 # database.  We then store that class in variable named Persisted; effectively,
 # we make a new class called Persisted.
-Persisted = declarative_base()  # pylint: disable=invalid-name
+Persisted = declarative_base()
 
 
 class Menu(Persisted):
     __tablename__ = 'menus'
     menu_id = Column(Integer, primary_key=True)  # primary keys default to auto_increment
     name = Column(String(256), nullable=False)  # nullable is the default
+    items = relationship('Item', uselist=True, back_populates='menu')
 
 
 class Item(Persisted):
@@ -24,12 +24,15 @@ class Item(Persisted):
     menu_id = Column(Integer, ForeignKey('menus.menu_id', ondelete='CASCADE'), nullable=False)
     name = Column(String(256), nullable=False)
     price = Column(Integer, nullable=False)
+    menu = relationship('Menu', back_populates='items')
+    order_items = relationship('OrderItem', uselist=True, back_populates='item')
 
 
 class Order(Persisted):
     __tablename__ = 'orders'
     order_id = Column(Integer, primary_key=True)
     timestamp = Column(DateTime)
+    order_items = relationship('OrderItem', uselist=True, back_populates='order')
 
 
 class OrderItem(Persisted):
@@ -37,6 +40,8 @@ class OrderItem(Persisted):
     order_id = Column(Integer, ForeignKey('orders.order_id', ondelete='CASCADE'), primary_key=True)
     item_id = Column(Integer, ForeignKey('items.item_id', ondelete='CASCADE'), primary_key=True)
     amount = Column(Integer)
+    item = relationship('Item', back_populates='order_items')
+    order = relationship('Order', back_populates='order_items')
 
 
 class DinerDatabase(object):

diner_installer.py

+from datetime import datetime
 from sys import stderr
 
 from sqlalchemy.exc import SQLAlchemyError
@@ -15,7 +16,7 @@ def add_starter_data(session):
     orange_juice = Item(menu=beverage_menu, name='Orange Juice', price=149)
     short_stack = Item(menu=food_menu, name='Pancakes', price=399)
     regular_pancakes = Item(menu=food_menu, name='Pancakes', price=499)
-    first_order = Order(order_items=[OrderItem(item=orange_juice, amount=2)])
+    first_order = Order(order_items=[OrderItem(item=orange_juice, amount=2)], timestamp=datetime.now())
     session.add(beverage_menu)
     session.add(food_menu)
     session.add(orange_juice)
@@ -26,17 +27,17 @@ def add_starter_data(session):
 
 def main():
     try:
-        url = DinerDatabase.construct_mysql_url('localhost', 3306, 'diner', 'root', 'cse1208')
+        url = DinerDatabase.construct_mysql_url('localhost', 3306, 'diner', 'root', 'mysqlpassword')
         diner_database = DinerDatabase(url)
         diner_database.ensure_tables_exist()
         print('Tables created.')
-        # session = diner_database.create_session()
-        # if already_has_data(session):
-        #     print('Not creating records because some already exist.')
-        # else:
-        #     add_starter_data(session)
-        #     session.commit()
-        #     print('Records created.')
+        session = diner_database.create_session()
+        if already_has_data(session):
+            print('Not creating records because some already exist.')
+        else:
+            add_starter_data(session)
+            session.commit()
+            print('Records created.')
     except SQLAlchemyError as exception:
         print('Database setup failed!', file=stderr)
         print(f'Cause: {exception}', file=stderr)