python 單例模式

編程中,有許多設計模式,在學習python中,第一次接觸到了單例模式.

單例模式應用場景:

同一個類中相同的方法和變量,由於需求,須要屢次建立.

屢次建立同一個實例,極大的浪費內存.

靜態方法,靜態變量.

注意:下面的代碼運行在py27版本中

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

簡單的web服務

 1 #!/usr/bin/env python
 2 # -*- coding:utf-8 -*-
 3 from wsgiref.simple_server import make_server
 4 import random
 5 class connPool:
 6     __instance =None
 7     def __init__(self):
 8         self.ip = '1.1.1.1'
 9         self.port = 3306
10         self.pwd = "123456"
11         self.username="root"
12         self.conList = [1,2,3,4,5,6,7,8,9]
13     @staticmethod
14     def getInstance():
15         if connPool.__instance:
16             return connPool.__instance
17         else:
18             connPool.__instance=connPool()
19             return connPool.__instance
20     def getConn(self):
21         #獲取鏈接
22         # print(self.conList)
23         res = random.randrange(1,11)
24         return res
25 def index():
26     # obj = connPool()  ##建立了多個實例
27     # print(obj)
28     p = connPool.getInstance() ##建立一個同一個實例/對象
29     print(p)
30     return "index11111"
31 def news():
32     return "news22222"
33 def RunServer(environ,start_response):
34     start_response(status="200 ok",headers=[('Content-Type','text/html')])
35     url=environ['PATH_INFO']
36     print(url)
37     if url.endswith("index"):
38         ret = index()
39         return ret
40     elif url.endswith("news"):
41         ret = news()
42         return ret
43     else:
44         return "404"
45     return "OldBoy xurui1"
46 if __name__ == '__main__':
47     httpd = make_server('',8000,RunServer)
48     print("Serving HTTP on port 8000....")
49     httpd.serve_forever() ##

單例模式代碼