python 单例模式

编程中,有许多设计模式,在学习python中,第一次接触到了单例模式.

单例模式应用场景:

同一个类中相同的方法和变量,因为需求,需要多次创建.

多次创建同一个实例,极大的浪费内存.

静态方法,静态变量.

注意:下面的代码运行在py27版本中

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from wsgiref.simple_server import make_server
def RunServer(environ,start_response):
    start_response(status="200 ok",headers=[('Content-Type','text/html')])
    url=environ['PATH_INFO']
    return "OldBoy xurui"
if __name__ == '__main__':
    httpd = make_server('',8000,RunServer)
    print("Serving HTTP on port 8000....")
    httpd.serve_forever()

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from wsgiref.simple_server import make_server
import random
class connPool:
    __instance =None
    def __init__(self):
        self.ip = '1.1.1.1'
        self.port = 3306
        self.pwd = "123456"
        self.username="root"
        self.conList = [1,2,3,4,5,6,7,8,9]
    @staticmethod
    def getInstance():
        if connPool.__instance:
            return connPool.__instance
        else:
            connPool.__instance=connPool()
            return connPool.__instance
    def getConn(self):
        #获取连接
        # print(self.conList)
        res = random.randrange(1,11)
        return res
def index():
    # obj = connPool()  ##创建了多个实例
    # print(obj)
    p = connPool.getInstance() ##创建一个同一个实例/对象
    print(p)
    return "index11111"
def news():
    return "news22222"
def RunServer(environ,start_response):
    start_response(status="200 ok",headers=[('Content-Type','text/html')])
    url=environ['PATH_INFO']
    print(url)
    if url.endswith("index"):
        ret = index()
        return ret
    elif url.endswith("news"):
        ret = news()
        return ret
    else:
        return "404"
    return "OldBoy xurui1"
if __name__ == '__main__':
    httpd = make_server('',8000,RunServer)
    print("Serving HTTP on port 8000....")
    httpd.serve_forever() ##