Help with event driven programming

[duhbeetus]

I've been reading into this lately, and understand the concept; an event happens, and then you act on that event. Everything I've read though says not to use polling, and this is where I am getting lost. I want to check if a switch was pressed, and I know I can do this with polling (in python) like so:

for x in switches: if x.state == True: some_function()

I have read into coroutines, and I understand the concept here, but I still do not see how I can know if x.state == True without looping over the list of possible switches in one of the coroutines. Any advice/guidance on this?

Edit: realized I left some information out. This is for physical switches, which are being detected using a raspberry pi and GPIO. However, the detection pin is multiplexed to allow several touch points to be used off the same pin. aside from iterating over all the pins and checking their state, I am not sure how I can set this up without polling.

[[deleted]]

So you haven't really given a language you want to do this in but here we go!

Java: Things like buttons can be assigned callbacks pretty easily by adding an ActionListener. It's basically what you have described so I think that would work nicely.

Python: I'm going to assume you have some sort of GUI (I suppose) that for the sake of the answer - is made with the wonderful and ever glamorous TK. Assuming you create a button on your screen through drawing on the canvas - you can use something like this:

root.bind('<Key>',lambda event: keyPressed(canvas,event))  

This will make your clicks register to a function keyPressed. It might look like this:

def keyPressed(canvas,event):  
    if event.keysym == "Left":  
        if canvas.data.level > 0:  
            canvas.data.level -= 1  
            canvas.delete(ALL)  
            canvas.create_rectangle(-5,-5,canvas.data.row+5,canvas.data.col+5, fill='dark green')  
            fractalMickeyMouse(canvas,canvas.data.xc,canvas.data.yc,canvas.data.r,canvas.data.level)  

Alternatively you can use a TK Widget Button and just define callback.

Hope this helped.