muhuk

asks

don't you (KDE users) feel all vulnerable and exposed without a good trash management system?

26 responses to this plurk

• 
  Dec 16, 2008 - 06:01PM

  shaf	nice to see ppl giving back to the community.. ps __trash_singleton ?? (!!)

• 
  Dec 16, 2008 - 06:01PM

  shaf	Have you worked than one out yet ?

• 
  Dec 16, 2008 - 06:18PM

  muhuk

  says

  shaf: that's very very old code. It was one of my first projects for learning python.

• 
  Dec 16, 2008 - 06:18PM

  muhuk

  says

  But it still works on my box New version is cooking, soon to be committed.

• 
  Dec 16, 2008 - 06:31PM

  shaf	asks if it's that simple to implement the singleton pattern in python

• 
  Dec 16, 2008 - 07:38PM

  muhuk

  says

  shaf: stackoverflow.com/questions/31875/is-there-a-simple-elegant-way-to-define-singletons-in-python

• 
  Dec 16, 2008 - 09:54PM

  timka.org

  says

  shaf: I use __new__ which always returns the single instance stored in a class attribute

• 
  Dec 16, 2008 - 09:58PM

  shaf	yeah but what's to stop you from executing the script using another python intepreter ? Singleton breaks.

• 
  Dec 16, 2008 - 09:59PM

  shaf	It's just that singleton is the simplest pattern to understand but can be tricky to implement if you don't understand your compiler/interptr

• 
  Dec 16, 2008 - 10:12PM

  timka.org

  says

  shaf: Another interpreter runs another instance of your program which has its own singleton instance.

• 
  Dec 16, 2008 - 10:45PM

  shaf

  exactly

• 
  Dec 16, 2008 - 10:55PM

  timka.org

  says

  shaf: I mean Singleton is usually limited to one process no matter what language you use, so multiple *program* instances is out of scope.

• 
  Dec 16, 2008 - 10:58PM

  shaf	timka_org yep. I know all this already. But as any good programmer would know, singleton in practice is not guarenteed

• 
  Dec 16, 2008 - 10:58PM

  shaf	this is why in any good production environment. Singleton is frowned upon

• 
  Dec 16, 2008 - 11:01PM

  shaf	especially read the last few paragraphs of this ... en.wikipedia.org/wiki/Singleton_pattern#Implementation

• 
  Dec 16, 2008 - 11:07PM

  timka.org

  says

  Yeah, in our production environment at work two instances of our app can fuck up the DB just because nobody cared about proper locking

• 
  Dec 16, 2008 - 11:10PM

  timka.org

  says

  It's about thread-safety inside single process, but you were talking about multiple processes

• 
  Dec 16, 2008 - 11:11PM

  shaf	hence the reason for me to have mixed feelings about it. If used - use it carefully

• 
  Dec 16, 2008 - 11:12PM

  shaf	well some idiot programmers assume singletons to work across processes too

• 
  Dec 16, 2008 - 11:14PM

  timka.org

  says

  Agree. And punish those who break the conventions!

• 
  Dec 16, 2008 - 11:18PM

  timka.org

  says

  I think you can only fire or train them. Hard choice...

• 
  Dec 17, 2008 - 07:22AM

  muhuk

  says

  on the other hand, most of the time singleton is not really needed in practice. Surely there is one trash (per user) but I have come to...

• 
  Dec 17, 2008 - 07:23AM

  muhuk

  says

  ...realize I don't need a singleton trash wrapper class at all. It is even making things harder to unittest.

• 
  Dec 17, 2008 - 07:24AM

  muhuk

  says

  Btw, a singleton shouldn't be confused as a concurrency mechanism (especially in multi-process systems).

• 
  Dec 17, 2008 - 07:34AM

  timka.org

  says

  Anyway, Singleton is just an object creation pattern, conceptually it has nothing to do with concurrency.

• 
  Dec 17, 2008 - 07:37AM

  timka.org

  says

  However, correct implementations must be aware of the used concurrency model