I'm wanting a paradigm in a Qt4 (PyQt4) program where a component is able to respond to a signal without knowing anything about where it is coming from.  
My intial reading suggests that I have to explicitly connect signals to slots. But what I want is for any of a number of components to be able to send a signal, and for it to be processed by another component. 
Comparing with another toolkits, for example, in wxWidgets I would use events. These automatically propogate up from child windows/objects to parents.  At each level they can be handled.  This means if I have a lot of children which may emit the same event, I don't have to explicitly connect all of them to the handler.  I can just put the handler in the parent, or some higher level in the window hierarchy.  This means that only the event generator and consumer need to know about the event at all.  The consumer doesn't need to know where the source of the event is, how many such sources there are, or anything else about it.
Is this possible in Qt - is there another approach?  Maybe there is an alternative event mechanism to signals and slots?
Don't you just want a good old fashioned method invocation?  The response is just the return value of the method.
How to broadcast a signal in Qt4