On Tue, Jan 20, 2009 at 1:03 AM, BlueBird <p...@freehackers.org> wrote: > On Jan 19, 4:10 am, Steven Woody <narkewo...@gmail.com> wrote: >> Hi, >> >> Python has Signal-Slot mechanism, > > Python does not have signal/slot mechanism. You are talking about the > Qt toolkit, which is initially a (nice) C++ toolkit, available also in > python via the PyQt wrapper. > > Signal/slots were introduced by Qt to make C++ gui programming easier. > Signal/slots basically provides a very easy way to implement the > observer/consumer design pattern, with only 2 or 3 lines of code (as > opposed to one or two classes in java for example). > > Python itself does not have signal/slots but the it's very easy to > emulate them using the Python language. In C++ however, it's tricky to > do signal/slots in pure C++ and this addition is one of the reason > that programming GUI in Qt is nice (personal opinion obviously). > > To comne back to your question: > >> why he still need another mechanism >> Event Handling? > > This is actually a Qt question: why have event handling for some > things, and signal/slot for some others ? > > My opinion on the debate: > - signal/slot add an overhead of one class to every QObject class, and > 3 method calls when emitting a signal (if I remember Qt documentation > correctly). For some real-time tasks, like repainting the screen, > every microseconds must be saved and sparing 3 method calls is a good > idea. > - since a GUI application is fundamentally an event driven system, the > event stuff has to be there anyway. > - signal/slot is very convenient for data exchange between widgets but > I think it would be overkill to use it everywhere. Event propagation > is a nice design as well. > > Now, if you want to discuss this further, I suggest to go to Qt > interest ( http://lists.trolltech.com/qt-interest/ ) which is > dedicated to discussion around Qt. > > cheers, > > Philippe > -- > http://mail.python.org/mailman/listinfo/python-list >
So much thanks, Philippe! -- http://mail.python.org/mailman/listinfo/python-list
