單例：專業用來處理連線多的問題（比如連線redis,zookeeper等），全域性只有一個物件

單例程式碼
def singleton(cls):
    
    instances = {}
    
    def _singleton(*args, **kwargs):
        if cls not in instances:
            instances[cls] = cls(*args, **kwargs)
        return instances[cls]
    
    return _singleton

例項程式碼

from singleton import singleton

#@singleton
class  MysqlOpers:
    
    def __init__(self):
        print('建立mysql連線')
        #虛擬碼  self.db = MySQLdb.connect()
        
    def select(self):
        pass
    
m = MysqlOpers()
n = MysqlOpers()
c = MysqlOpers()

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

加上單例裝飾器後

mysql 連線池

#coding=utf-8

import traceback

import MySQLdb
from DBUtils.PooledDB import PooledDB


db_pool_ins = None

#需要替換使用者名稱，密碼等
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():
    #連線池物件
    def __init__(self):
        #建立和資料庫系統的連線
        global db_pool_ins
        if db_pool_ins == None:
            db_pool_ins = DBPool()
        self.conn = db_pool_ins.get_connection()
        #獲取操作遊標
        self.cursor = self.conn.cursor()

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

    def data_operate(self, sql, params=()):
        '''
        資料的插入，更新，刪除
        :param database:
        :param sql:
        :return: 成功：0，失敗：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=()):
        '''
        資料的插入，更新，刪除
        :param sql:
        :param params:
        :return: 成功：0，失敗：1
        '''
        #執行sql語句
        self.cursor.executemany(sql, params)
        #提交到資料庫執行
        self.conn.commit()

    def data_operate_count(self, sql, params=()):
        '''
        資料的插入，更新，刪除
        :return: 受影響的條數
        '''
        #執行sql語句
        count = self.cursor.execute(sql, params)
        #提交到資料庫執行
        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()

使用

from mysql import DBAction

dba = DBAction()
ret = dba.data_inquiry_all("SELECT * FROM friend")
print(ret)