python 单例与数据库连接池 及相关选择

单例：专业用来处理连接多的问题（比如连接redis,zookeeper等），全局只有一个对象

单例代码
def singleton(cls):

    instances = {}

    def _singleton(*args, **kwargs):
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]

    return _singleton

　　

实例代码

from singleton import singleton

#@singleton
class  MysqlOpers:

    def __init__(self):
        print('建立mysql连接')
        #伪代码  self.db = MySQLdb.connect()

    def select(self):
        pass

m = MysqlOpers()
n = MysqlOpers()
c = MysqlOpers()

print(id(m))
print(id(n))
print(id(c))

加上单例装饰器后

mysql 连接池

#coding=utf-8

import traceback

import MySQLdb
from DBUtils.PooledDB import PooledDB

db_pool_ins = None

#需要替换用户名，密码等
class DBPool():
    def __init__(self):
        self.pool = PooledDB(creator=MySQLdb, mincached=1, maxcached=10, maxconnections=100, blocking=True,
                             host= "127.0.0.1", port=3306, user='', passwd='',
                             db='test', charset='utf8',)

    def get_connection(self):
        return self.pool.connection()

class DBAction():
    #连接池对象
    def __init__(self):
        #建立和数据库系统的连接
        global db_pool_ins
        if db_pool_ins == None:
            db_pool_ins = DBPool()
        self.conn = db_pool_ins.get_connection()
        #获取操作游标
        self.cursor = self.conn.cursor()

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

    def data_operate(self, sql, params=()):
        '''
        数据的插入，更新，删除
        :param database:
        :param sql:
        :return: 成功：0，失败：1
        '''
        try:
            self.cursor.execute(sql, params)
            self.conn.commit()
            return 0
        except:
            print("sql is %s, params is %s error. %s" % (sql, params, traceback.format_exc()))
            self.conn.rollback()
            raise Exception

    def data_operate_many(self, sql, params=()):
        '''
        数据的插入，更新，删除
        :param sql:
        :param params:
        :return: 成功：0，失败：1
        '''
        #执行sql语句
        self.cursor.executemany(sql, params)
        #提交到数据库执行
        self.conn.commit()

    def data_operate_count(self, sql, params=()):
        '''
        数据的插入，更新，删除
        :return: 受影响的条数
        '''
        #执行sql语句
        count = self.cursor.execute(sql, params)
        #提交到数据库执行
        self.conn.commit()
        return count

    def data_inquiry(self, sql, size=10, params=()):
        '''
        :param database:
        :param sql:
        :return: ((),(),...,())
        '''
        self.cursor.execute(sql, params)
        result = self.cursor.fetchmany(size)
        return result

    def data_inquiry_all(self, sql, params=()):
        '''
        :param database:
        :param sql:
        :return: ((),(),...,())
        '''
        self.cursor.execute(sql, params)
        result = self.cursor.fetchall()

        return result

    def commit(self):
        self.conn.commit()

　　链接mysql等关系型数据库，应当采用此方式。确保多连接存在。