Python and the Singleton Pattern

[Moshe Zadka]

On Tue, 6 Apr 1999, Neelakantan Krishnaswami wrote:

> Isn't it possible to make use of Python's dynamism to turn any 
> class into a singleton class, as needed?

<snipped implementation of class Singletonizer, which is basically a 
class into a factory-function-which-always-returns the same object>

The problem with that, of course, is that it makes inheritance from 
a singleton class impossible. 

How about:

class MySingleton:
	class _my_dummy: pass
	_dummy=_my_dummy()
	_initialized=0
	def __init__(self, ....):
		if initialized: return
		......
	def __getattr__(self, attr):
		return _dummy.__dict__[attr]

	def __setattr__(self, attr, val):
		_dummy.__dict__[attr]=val

(I haven't tested it, but is seems like it should work)
--
Moshe Zadka <mzadka at geocities.com>. 
QOTD: What fun to me! I'm not signing permanent.