python中实现mysql连接池

import pymysql
from DBUtils.PooledDB import PooledDB

MYSQL_HOST = 'localhost'
USER = 'root'
PASSWORD = 'root'
DB = 'python3'
PORT = 3306

pool = PooledDB(pymysql, 5, host=MYSQL_HOST, user=USER, passwd=PASSWORD, db=DB, port=PORT)  # 5为连接池里的最少连接数

conn = pool.connection()  # 以后每次需要数据库连接就是用connection（）函数获取连接就好了
cur = conn.cursor()
SQL = "select * from url_file_path500 limit 3"
r = cur.execute(SQL)
re = cur.fetchall()
print(re)
cur.close()
conn.close()
import pymysql
from DBU