python singleton

 1 def singleton(cls):
 2     instance = {}
 3     def returnInstance():
 4         if cls not in instance:
 5             instance[cls] = cls()
 6         return instance[cls]
 7     return returnInstance
 8 
 9 @singleton
10 class MyClass(object):
11     def __init__(self):
12         self.x = 2
13 
14 a = MyClass()
15 b = MyClass()
16 
17 print a==b