Ole Streicher wrote: > Hi Peter, > > Peter Otten <__pete...@web.de> writes: >> Ole Streicher wrote: >>> Peter Otten <__pete...@web.de> writes: >>>>> What I want is to have a universal class that "always" works: with >>>>> unbound functions, with bound function, with lambda expressions, with >>>>> locally defined functions, >>>> That's left as an exercise to the reader ;) >>> Do you have the feeling that there exists any reader that is able to >>> solve this exercise? :-) >> I was thinking of you. > > I could imagine that. However, I am just a beginner in Python and I dont > know which types "callables" there exist in python and which "smart" > ideas (like re-creating them at every call) additionally occur when I > implement such a beast. For example, for locally defined functions, I > have still no idea at all on how to keep them away from the garbage > collector. > >>> I am a bit surprised that already such a simple problem is virtually >>> unsolvable in python.
Btw, have you implemented such a design in another language? >>> Do you think that my concept of having a DoAsync >>> class is wrong? >> I don't understand the example you give in the other post. > > Hmm. I am programming a GUI client application. The client will receive > some input data (via network, and via user input) and shall be updated > after these data. > > Unfortunately, the input data (and ofcourse the user input) do not come > regularly; there may times when the data come too fast to process all > of them. > > Imagine, for example, that I want to provide a 2d-gaussian fit to some > region of an image and display the result in a separate window, and > updated this whenever the mouse is moved. > > The fit takes (let's say) some seconds, so I cannot just call the fit > routine within the mouse move event (this would block other gui > operations, and f.e. the display of the mouse coordinates). So I need > just to trigger the fit routine on mouse movement, and to check > afterwards whether the mouse position is still current. > > This is the reason for the DoAsync class: when it is called, it shall > trigger the function that was given in the constructor, t.m. > > class MyClass: > def __init__(self): > self.update_fit = DoAsync(update_the_fit) > > def mouse_move(self, event): > self.set_coordinates(event.x, event.y) > self.update_fit() # trigger the update_the_fit() call > ... > > Thus, the mouse_move() method is fast, even if the update_the_fit() > method takes some time to process. > > I want to implement it now that DoAsync will be automatically garbage > collected whenever the MyClass object is deleted. Since DoAsync starts > its own thread (which only shall finish when the MyClass object is > deleted), a reference to MyClass (or one of its functions) will keep the > MyClass object from garbage collection. > >> If you are trying to use reference counting as a means of inter-thread >> communication, then yes, I think that's a bad idea. > > No; my problem is: > > - a thread started in DoAsync will keep the DoAsync object from > garbage collection > - a reference to a MyClass realted object (the bound method) in DoAsync > will thus also prevent the MyClass object from garbage collection > - Even if I dont use the MyClass object anymore, and nobody else uses > the DoAsync object, both stand in memory forever, and the thread also > never finishes. I think I'd go for a simpler approach, manage the lifetime of MyClass instances manually and add a MyClass.close() method that sets a flag which in turn is periodically read by DoAsync() and will eventually make it stop. Peter -- http://mail.python.org/mailman/listinfo/python-list
