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SingletonProgramming - PythonInfo Wiki
User
Singleton
See also https://c2.com/cgi/wiki?PythonSingleton and https://www.python.org/workshops/1997-10/proceedings/savikko.html
classmethod
pro
- You can use both as simple class or as a singleton.
- You do not need to write code for each class you want to act as singleton.
cons
1 # Code is Public Domain.
2 class Singleton:
3 _singleton = None
4 def getSingleton(cls):
5 if not isinstance(cls._singleton,cls):
6 cls._singleton = cls()
7 return cls._singleton
8
9 getSingleton = classmethod(getSingleton)
10
11 if __name__=='__main__':
12 class Test(Singleton):
13 def test(self):
14 print self.__class__,id(self)
15
16 class Test1(Test):
17 def test1(self):
18 print self.__class__,id(self),'Test1'
19
20 t1 = Test.getSingleton()
21 t2 = Test.getSingleton()
22
23 t1.test()
24 t2.test()
25 assert(isinstance(t1,Test))
26 assert(isinstance(t2,Test))
27 assert(id(t1)==id(t2))
28
29 t1 = Test1.getSingleton()
30 t2 = Test1.getSingleton()
31
32 assert(isinstance(t1,Test1))
33 assert(isinstance(t2,Test1))
34 assert(id(t1)==id(t2))
35
36 t1.test()
37 t1.test1()
38 t2.test()
39 t1.test1()
40
41 t3 = Test.getSingleton()
42
43 t3.test()
44 assert(isinstance(t3,Test))
SingletonProgramming (last edited 2008-11-15 14:00:11 by localhost)