db游标上的Python ReferenceError

如何解决db游标上的Python ReferenceError

我似乎无法找到为什么我的数据库光标出现参考错误。出于某种原因，de GC会清理游标对象。这就是我目前使用的所有代码。调用__del__时会引发参考错误。这是我目前的代码：

import mysql.connector
from mysql.connector import errorcode
import enum
from datetime import datetime


class ScrapeType(enum.Enum):
    FULL = 1
    SINGLE = 2


class BaseScraper:
    db_config = {

    }

    user_agents = []
    cnx = None
    cursor = None
    store_id = None
    scrape_history_id = None
    scrape_error = 0

    def __init__(self,store,scrape_type):
        try:
            self.cnx = mysql.connector.connect(**self.db_config)
            self.cursor = self.cnx.cursor(dictionary=True)
            print("Setting store Id.")
            self.get_store_id(store)
            if self.store_id is None or len(self.store_id) == 0:
                raise ValueError("Store not found")
            else:
                self.store_id = self.store_id["Id"]

            self.init_scrape_history(scrape_type)
        except mysql.connector.Error as err:
            if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
                self.add_scrape_error("Something is wrong with your user name or password")
            elif err.errno == errorcode.ER_BAD_DB_ERROR:
                self.add_scrape_error("Database does not exist")
            else:
                self.add_scrape_error(err)

    def __del__(self):
        self.finish_scrape_history()
        self.cursor.close()
        self.cnx.close()

    def add_scrape_error(self,message,product_id=None,):
        query = ("INSERT INTO ScrapeErrors"
                 "(scrape_id,product_id,message)"
                 "VALUES (%s,%s,%s)")
        self.write_to_db(query,(self.scrape_history_id,))
        self.scrape_error += 1

    def init_scrape_history(self,scrape_type):
        self.cursor.execute('SELECT UUID()')
        self.scrape_history_id = self.cursor.fetchone()["UUID()"]
        query = ("INSERT INTO ScrapeHistory "
                 "(Id,store_id,scrape_type) "
                 "VALUES (%s,self.store_id,scrape_type.value,))

    def finish_scrape_history(self):
        query = "UPDATE ScrapeHistory SET end_date= %s,error_count= %s WHERE Id = %s"
        self.write_to_db(query,(datetime.now(),self.scrape_error,self.scrape_history_id,))

    def is_price_changed(self,price):
        self.cursor.execute("SELECT price FROM Product WHERE Id = %s AND store_id = %s ORDER BY last_updated DESC ",(product_id,))
        result = self.cursor.fetchall()
        if len(result) > 0:
            return result[0]["price"] != price
        else:
            return True

    # We already checked for null when calling this.
    def add_product(self,name,image,price,bonus):
        # Price is in cents.
        price_in_cents = int(str(price).ljust(4,"0"))
        # Only write new record if price has changed. Safes db space.
        if self.is_price_changed(product_id,price_in_cents):
            query = ("INSERT INTO Product (Id,bonus) "
                     "VALUES (%s,%s)")
            product = (product_id,price_in_cents,bonus)
            self.write_to_db(query,product)

    def get_store_id(self,store_name):
        self.cursor.execute("SELECT Id FROM GroceryStore WHERE store_name = %s",(store_name,))
        self.store_id = self.cursor.fetchone()

    # TODO: error/logging do we want it here or not?
    def write_to_db(self,query,data):
        try:
            self.cursor.execute(query,data)
            self.cnx.commit()
            return self.cursor,self.cnx
        except mysql.connector.Error as e:
            try:
                self.add_scrape_error("MySQL Error [%d]: %s" % (e.args[0],e.args[1]))
            except IndexError:
                self.add_scrape_error("MySQL Error: %s" % str(e))

解决方法

您必须放置config变量（more options）

db_config = {
'host': 'localhost','user': 'root','passwd':'testpaword','database':'testschema'
}

课外。您不能在BaseScraper类中定义它。

然后您可以运行代码