Hasta La Motion!

I am not quite sure what I am actually after … so I am having difficulties to to look/find anything. Maybe if I try explaining someone can give me a hint 🙂

I want to run a python script on every frame. Or feed it with some value on every frame. Updating the values live … or something like that.

For example when I hit play I want the size of a blur to be 1 on frame 1. Then on frame 2 the blur is 2. So the blur size equals the current frame.

As an expression this would be simple, but I don’t know how to do this in python.

If I do:
num = nuke.frame()
nuke.toNode(‘Blur1’).knob(‘size’).setValue(num)

Nuke then sets the size to the frame that I launch the script and keeps that value. How do I get it to update the value for every frame?

Any help appreciated
Cheers