解决MySQL报ValueError(“Could not process parameters“)错误
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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：
- 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 None
else:
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 None
else:
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.pooling
class DataBaseInfo(object):
def __init__(self, host='127.0.0.1', port='3306', user='root', password='xxx', database='chair'):
self.host = host
self.port = port
self.user = user
self.password = password
self.database = database
def 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_list
class 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 = host
self.port = port
self.user = user
self.password = password
self.database = database
res =
res["host"] = self.host
res["port"] = self.port
res["user"] = self.user
res["password"] = self.password
res["database"] = self.database
self.dbconfig = res
self.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 pool
def 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 None
else:
res = cursor.fetchall()
self.close(conn, cursor)
return res
def 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 None
else:
res = cursor.fetchall()
self.close(conn, cursor)
return res
def 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, Upasswd
sql = "insert into login (Uname, Upasswd) values (%s, %s)"
bRes = self.dbPool.execute(sql, args, commit=True)
return bRes
def 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 False
return bRes
def selectName(self, name):
args = name
sql = "SELECT * FROM login WHERE Uname=%s"
res = self.dbPool.execute(sql, args,False)
return res
def selectAll(self):
sql = "SELECT * FROM login"
res = self.dbPool.execute(sql)
return res
def isExisted(self, Uname):
strLen = len(str(self.selectTable(Uname)))
if strLen > 4:
return True
else:
return False
def updatePassword(self, Uname, Upasswd):
sql = "UPDATE login SET Upasswd=%s where Uname=%s;"
args = Upasswd, Uname
res = self.dbPool.execute(sql, args, commit=True)
bRes = True if res is None else False
return 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 Transfer
Source Server : locaLWin10
Source Server Type : MySQL
Source Server Version : 50733
Source Host : localhost:3306
Source Schema : chair
Target Server Type : MySQL
Target Server Version : 50733
File Encoding : 65001
Date: 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 LoginTable
dbconfig =
"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：
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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