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
