解决MySQL报ValueError(“Could not process parameters“)错误

在使用Python连接MySQL数据库时，有时报"ValueError(“Could not process parameters”)"错误，如图(1)所示：

图(1) MySQL报"ValueError("Could not process parameters)"错误

首先排查，代码里的字段是否与数据库的字段保持一致(区分大小写);
再排查，函数调用时的字段顺序，是否与声明时的字段顺序保持一致；

如果上面2项都是一致的(即已排除)，那么很可能是下面的原因:

出现该问题的原因是：传参时没有使用元组的方式，造成MySQL无法解析而报错。
解决方法：使用元组的方式传入数据库。

1、修改前

    def execute(self, sql, args=None, commit=False):conn = self.pool.get_connection()cursor = conn.cursor()if args:cursor.execute(sql, args) ## 此处有问题else:cursor.execute(sql)if commit is True:conn.commit()self.close(conn, cursor)return Noneelse:res = cursor.fetchall()self.close(conn, cursor)return res

2、修复Bug

    def execute(self, sql, args=None, commit=False):conn = self.pool.get_connection()cursor = conn.cursor()if args:cursor.execute(sql, (args,) ) ## 要用元组的方式传参，即使用(arg,)else:cursor.execute(sql)if commit is True:conn.commit()self.close(conn, cursor)return Noneelse:res = cursor.fetchall()self.close(conn, cursor)return res

附录

3.1 MySQL数据库连接池基类

创建数据库连接池基类，命名为base.py，默认支持5个connect连接。
//base.py

import pymysql
import mysql.connector.poolingclass DataBaseInfo(object):def __init__(self, host='127.0.0.1', port='3306', user='root', password='xxx', database='chair'):self.host = hostself.port = portself.user = userself.password = passwordself.database = databasedef start_mysql(self):db = pymysql.connect(self.host, self.port, self.user, self.password, self.dbname)cursor = db.cursor()table_list = [db, cursor]return table_listclass DataBasePool(object):def __init__(self, host='127.0.0.1', port='3306', user='root', password='xxx', database='chair',pool_name='mypool', pool_size=5):self.host = hostself.port = portself.user = userself.password = passwordself.database = databaseres = {}res["host"] = self.hostres["port"] = self.portres["user"] = self.userres["password"] = self.passwordres["database"] = self.databaseself.dbconfig = resself.pool = self.create_pool(pool_name=pool_name, pool_size=pool_size)def create_pool(self, pool_name="mypool", pool_size=5):pool = mysql.connector.pooling.MySQLConnectionPool(pool_name=pool_name,pool_size=pool_size,pool_reset_session=True,**self.dbconfig)return pooldef close(self, conn, cursor):cursor.close()conn.close()def execute(self, sql, args=None, commit=False):conn = self.pool.get_connection()cursor = conn.cursor()if args:cursor.execute(sql, (args,))else:cursor.execute(sql)if commit is True:conn.commit()self.close(conn, cursor)return Noneelse:res = cursor.fetchall()self.close(conn, cursor)return resdef executemany(self, sql, args, commit=False):conn = self.pool.get_connection()cursor = conn.cursor()cursor.executemany(sql, args)if commit is True:conn.commit()self.close(conn, cursor)return Noneelse:res = cursor.fetchall()self.close(conn, cursor)return resdef executeRead(self, sql, args):conn = self.pool.get_connection()cursor = conn.cursor()cursor.executemany(sql, args)res = cursor.fetchall()self.close(conn, cursor)myData = []for row in res:myData.append(row)return myData

3.2 读写某个Table

这里以读写chair数据库里的login表格为例，进行说明。
//loginTable.py

from .base import DataBasePool# dbconfig = {#     "host": "127.0.0.1",
#     "port": "3306",
#     "user": "root",
#     "password": "xxx",
#     "database": "chair",
#     "pool_name": "mypool",
#     "pool_size": 5
# }class LoginTable(object):def __init__(self, dbConf):self.host = dbConf['host']self.port = dbConf['port']self.user = dbConf['user']self.password = dbConf['password']self.database = dbConf['database']self.pool_name = dbConf['pool_name']self.pool_size = int(dbConf['pool_size'])self.dbPool = DataBasePool(self.host, self.port, self.user, self.password,self.database, self.pool_name, self.pool_size)def insertTable(self, Uname, Upasswd):args = Uname, Upasswdsql = "insert into login (Uname, Upasswd) values (%s, %s)"bRes = self.dbPool.execute(sql, args, commit=True)return bResdef hasTable(self):sql = "SELECT table_name FROM information_schema.TABLES WHERE table_name='login'"strLen = len(str(self.dbPool.execute(sql)))bRes = True if strLen > 4 else Falsereturn bResdef selectName(self, name):args = namesql = "SELECT * FROM login WHERE Uname=%s"res = self.dbPool.execute(sql, args,False)return resdef selectAll(self):sql = "SELECT * FROM login"res = self.dbPool.execute(sql)return resdef isExisted(self, Uname):strLen = len(str(self.selectTable(Uname)))if strLen > 4:return Trueelse:return Falsedef updatePassword(self, Uname, Upasswd):sql = "UPDATE login SET Upasswd=%s where Uname=%s;"args = Upasswd, Unameres = self.dbPool.execute(sql, args, commit=True)bRes = True if res is None else Falsereturn bRes

3.3 创建login表格

在Navicat里，导入login.sql文件，即可创建login表格。
//login.sql

/*Navicat Premium Data TransferSource Server         : locaLWin10Source Server Type    : MySQLSource Server Version : 50733Source Host           : localhost:3306Source Schema         : chairTarget Server Type    : MySQLTarget Server Version : 50733File Encoding         : 65001Date: 11/04/2022 22:54:41
*/SET NAMES utf8mb4;
SET FOREIGN_KEY_CHECKS = 0;-- ----------------------------
-- Table structure for login
-- ----------------------------
DROP TABLE IF EXISTS `login`;
CREATE TABLE `login`  (`Uname` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NOT NULL,`Upasswd` varchar(255) CHARACTER SET utf8mb4 COLLATE utf8mb4_general_ci NULL DEFAULT NULL,PRIMARY KEY (`Uname`) USING BTREE
) ENGINE = InnoDB CHARACTER SET = utf8mb4 COLLATE = utf8mb4_general_ci ROW_FORMAT = Dynamic;-- ----------------------------
-- Records of login
-- ----------------------------
INSERT INTO `login` VALUES ('hua', '111');
INSERT INTO `login` VALUES ('Jerry', '222');
INSERT INTO `login` VALUES ('root', '333');
INSERT INTO `login` VALUES ('Tom', '555');SET FOREIGN_KEY_CHECKS = 1;

3.4 测试login表格

读取login表格里某个用户比如Tom，测试代码如下：
//doUser.py

from .loginTable import LoginTabledbconfig = {"host": "localhost","port": "3306","user": "root","password": "xxx","database": "chair","pool_name": "mypool","pool_size": 5
}myTab = LoginTable(dbconfig)res = myTab.selectName('Tom')
print('res:', res)

效果如下：

图(2) 成功读取login里的Tom信息

3.5 MySQL连接池依赖包

MySQL连接池有2个依赖包，如下:

pip install mysql-connector-python==8.0.27
pip install pymysql==1.0.2

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