SQLAlchemy Core中的异常及事务处理样码

#coding=utf-8

from datetime import datetime
from sqlalchemy import (MetaData, Table, Column, Integer, Numeric, String, Boolean, 
                        DateTime, ForeignKey, ForeignKey, create_engine, CheckConstraint)
from sqlalchemy import (insert, select, update, delete, text, desc, cast, and_, or_, not_)
from sqlalchemy.sql import func
from sqlalchemy.exc import IntegrityError

metadata = MetaData()

cookies = Table(‘cookies‘, metadata,
                Column(‘cookie_id‘, Integer(), primary_key=True),
                Column(‘cookie_name‘, String(50), index=True),
                Column(‘cookie_recipe_url‘, String(255)),
                Column(‘cookie_sku‘, String(55)),
                Column(‘quantity‘, Integer()),
                Column(‘unit_cost‘, Numeric(12, 2)),
                CheckConstraint(‘quantity >= 0‘, name=‘quantity_positive‘)
                )

users = Table(‘users‘, metadata,
              Column(‘user_id‘, Integer(), primary_key=True),
              Column(‘username‘, String(15), nullable=False, unique=True),
              Column(‘email_address‘, String(255), nullable=False),
              Column(‘phone‘, String(20), nullable=False),
              Column(‘password‘ ,String(25), nullable=False),
              Column(‘created_on‘, DateTime(), default=datetime.now),
              Column(‘updated_on‘, DateTime(), default=datetime.now, onupdate=datetime.now)
              )

orders = Table(‘orders‘, metadata,
               Column(‘order_id‘, Integer(), primary_key=True),
               Column(‘user_id‘, ForeignKey(‘users.user_id‘)),
               Column(‘shipped‘, Boolean(), default=False)
               )

line_items = Table(‘line_items‘, metadata,
                   Column(‘line_items_id‘, Integer(), primary_key=True),
                   Column(‘order_id‘, ForeignKey(‘orders.order_id‘)),
                   Column(‘cookie_id‘, ForeignKey(‘cookies.cookie_id‘)),
                   Column(‘quantity‘, Integer()),
                   Column(‘extended_cost‘, Numeric(12, 2))
                   )

engine = create_engine(‘mysql+pymysql://u:p@ip:3306/cookies‘)
metadata.create_all(engine)
connection = engine.connect()

def ship_it(order_id):
    s = select([line_items.c.cookie_id, line_items.c.quantity])
    s = s.where(line_items.c.order_id == order_id)
    transaction = connection.begin()
    cookies_to_ship = connection.execute(s)
    try:
        for cookie in cookies_to_ship:
            u = update(cookies).where(cookies.c.cookie_id==cookie.cookie_id)
            u = u.values(quantity = cookies.c.quantity - cookie.quantity)
            result = connection.execute(u)
        u = update(orders).where(orders.c.order_id == order_id)
        u = u.values(shipped=True)
        result = connection.execute(u)
        print("Shipped order ID: {}".format(order_id))
        transaction.commit()
    except IntegrityError as error:
        transaction.rollback()
        print(error)

‘‘‘
ins = insert(users).values(
    username="cookiemon",
    email_address="mon@cookie.com",
    phone="111-111-1111",
    password="password"
    )
try:
    result = connection.execute(ins)
except IntegrityError as error:
    pass

ins = cookies.insert()
inventory_list = [
    {
        ‘cookie_name‘: ‘chocolate chip‘,
        ‘cookie_recipe_url‘: ‘http://some.aweso.me/cookie/recipe.html‘,
        ‘cookie_sku‘: ‘CC01‘,
        ‘quantity‘: ‘12‘,
        ‘unit_cost‘: ‘0.50‘
    },
    {
        ‘cookie_name‘: ‘dark chocolate chip‘,
        ‘cookie_recipe_url‘: ‘http://some.aweso.me/cookie/recipe_dark.html‘,
        ‘cookie_sku‘: ‘CC02‘,
        ‘quantity‘: ‘1‘,
        ‘unit_cost‘: ‘0.75‘
    }
    ]
result = connection.execute(ins, inventory_list)


ins = insert(orders).values(user_id=1, order_id=‘1‘)
result = connection.execute(ins)
ins = insert(line_items)
order_items = [
    {
        ‘order_id‘: 1,
        ‘cookie_id‘: 1,
        ‘quantity‘: 9,
        ‘extended_cost‘: 4.50
    }
    ]
result = connection.execute(ins, order_items)


ins = insert(orders).values(user_id=1, order_id=‘2‘)
result = connection.execute(ins)
ins = insert(line_items)
order_items = [
    {
        ‘order_id‘: 2,
        ‘cookie_id‘: 1,
        ‘quantity‘: 4,
        ‘extended_cost‘: 1.50
    },
    {
        ‘order_id‘: 2,
        ‘cookie_id‘: 2,
        ‘quantity‘: 1,
        ‘extended_cost‘: 4.50
    }
    ]
result = connection.execute(ins, order_items)

ship_it(1)
s = select([cookies.c.cookie_name, cookies.c.quantity])
connection.execute(s).fetchall()
‘‘‘
ship_it(20)