Advanced Search

Making Daniel Brodie's singleton recipe work with keyword arguments

/ Published in: Python
Save to your folder(s)
The ASPN cookbook has many recipes for singletons in Python. So far, this one
http://aspn.activestate.com/ASPN/Cookbook/Python/Recipe/412551
has been my favourite, because it is so simple and concise. However, I just ran into a brick wall when I tried to use it with a class that can be initialized with keyword arguments. This is my first draft for a solution to this problem. It's quick and dirty; please give it a glance and leave a comment if you find a problem.

Expand | Embed | Plain Text

Copy this code and paste it in your HTML 
  1. class Singleton(type):
  2.     def __init__(self, *args, **kwds):
  3.         type.__init__(self, *args, **kwds)
  4.         self._instances = {}
  5.  
  6.     def __call__(self, *args, **kwds):
  7.         sig = args + tuple(sorted(kwds.items()))
  8.         if not sig in self._instances:
  9.             self._instances[sig] = type.__call__(self, *args, **kwds)
  10.         return self._instances[sig]

Report this snippet


Comments

RSS Icon Subscribe to comments

You need to login to post a comment.