当有多个请求发起，就需要用到数据库连接池

import pymysql
from conf import setting
from DBUtils.PooledDB import PooledDB

POOL = PooledDB(
    creator=pymysql,  # 使用链接数据库的模块
    maxconnections=6,  # 连接池允许的最大连接数，0和None表示不限制连接数
    mincached=6,  # 初始化时，链接池中至少创建的空闲的链接，0表示不创建
    maxcached=5,  # 链接池中最多闲置的链接，0和None不限制
    maxshared=3,
    # 链接池中最多共享的链接数量，0和None表示全部共享。
    blocking=True,  # 连接池中如果没有可用连接后，是否阻塞等待。True，等待；False，不等待然后报错
    maxusage=None,  # 一个链接最多被重复使用的次数，None表示无限制
    setsession=[],  # 开始会话前执行的命令列表。
    ping=0,
    # ping MySQL服务端，检查是否服务可用。

    host=setting.host,
    port=setting.port,
    user=setting.user,
    password=setting.password,
    database=setting.database,
    charset=setting.charset,
    autocommit=setting.autocommit
)

import pymysql
from ormpool import db_pool
from threading import current_thread


class MysqlPool:
    def __init__(self):
        self.conn = db_pool.POOL.connection()
        # print(db_pool.POOL)
        # print(current_thread().getName(), '拿到连接', self.conn)
        # print(current_thread().getName(), '池子里目前有', db_pool.POOL._idle_cache, '\r\n')
        self.cursor = self.conn.cursor(cursor=pymysql.cursors.DictCursor)

    def close_db(self):
        self.cursor.close()
        self.conn.close()

    def select(self, sql, args=None):
        self.cursor.execute(sql, args)
        rs = self.cursor.fetchall()
        return rs

    def execute(self, sql, args):

        try:
            self.cursor.execute(sql, args)
            affected = self.cursor.rowcount
            # self.conn.commit()
        except BaseException as e:
            print(e)
        finally:
            self.close_db()
        return affected

当然不能每次都请求来开一次数据库连接池，那就没有池的意义了，这就需要用到python中的单例

from conf import setting
import pymysql


class Mysql:
    __instance = None
    def __init__(self):
        self.conn = pymysql.connect(host=setting.host,
                                    user=setting.user,
                                    password=setting.password,
                                    database=setting.database,
                                    charset=setting.charset,
                                    autocommit=setting.autocommit)
        self.cursor = self.conn.cursor(cursor=pymysql.cursors.DictCursor)

    def close_db(self):
        self.conn.close()

    def select(self, sql, args=None):
        self.cursor.execute(sql, args)
        rs = self.cursor.fetchall()
        return rs

    def execute(self, sql, args):
        try:
            self.cursor.execute(sql, args)
            affected = self.cursor.rowcount
            # self.conn.commit()
        except BaseException as e:
            print(e)
        return affected

    @classmethod
    def singleton(cls):
        if not cls.__instance:
            cls.__instance = cls()
        return cls.__instance