import pymysql

#todo 单点连接数据库

pd = pymysql.connect(host=‘127.0.0.1‘,port=3306,user=‘root‘,passwd=‘123456‘,db=‘test‘,charset=‘utf8‘)
cursor = pd.cursor()
sql = ‘select * from class‘
cursor.execute(sql)
class_data = cursor.fetchall()
print(class_data)
cursor.close()
pd.cursor()

import pymysql
#todo 数据库连接池连接数据库
from DBUtils.PooledDB import PooledDB

pool_db = PooledDB(pymysql,5,host=‘127.0.0.1‘,port=3306,user=‘root‘,passwd=‘123456‘,db=‘test‘,charset=‘utf8‘)
#5为连接池里的最少连接数
coon = pool_db.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
cursor = coon.cursor()
sql = ‘select * from class‘
cursor.execute(sql)
class_data = cursor.fetchall()
print(class_data)