scrapy中连接mysql

class BizhiPipeline_MySQL(object):
    def open_spider(self,spider):
        # 创建数据库连接
        self.conn = pymysql.connect(host='localhost', user='root', password='he1234', database='picture')
        # 创建游标对象
        self.cursor = self.conn.cursor()
    def process_item(self,item,response):
        global a
        # sql语句
        insert_sql = """
                insert into ONE_PICTURE(id,content) VALUES (%s,%s)
                """
        # 插入到数据库
        self.cursor.execute(insert_sql,(item['a'],item['picture_content']))
        # 提交数据
        self.conn.commit()

    def close_spider(self, spider):
        # 关闭游标和连接
        self.cursor.close()
        self.conn.close()