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)

 

SQLAlchemy Core中的异常及事务处理样码

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