How to combine in node tree two inputs without sockets and connect them into one input?
I was trying to make a driver but all data paths are always wrong and change nothing but default value not values I nedeed.
When I use console window it works only when I type paths, and it doesn’t in drivers editor…
Confuised.
Drivers and nodes might not work that well together. If they do happen to work I would check if they update properly before rendering in all situations - there could be issues. I would try getting away with nodes only, Maybe you can atchieve similar result using other nodes?
Anyway, why don’t you connect it to Size socket of the Blur node if the values need to be combined?
Yes, thank you, I think this is the only way to manipulate them properly
It’s still a pitty it’s programmed this way. I think there should be no values in nodes that are not exposed to sockets. Unfortunately there are a few cases with nodes that make no sense at all. 
Thought it would be possible to turn those inputs into sockets, in terms of computing it can be difficult to decide what the user really wants to do. For example, my ‘loop’ node has an iterator count that I deliberately choose to not have a socket for it, mainly because it makes no sense at all to have some value for some samples, and another value for other samples.
@OP: Anyway, if carefully used you can expose those values to the nodegroup interface through python (i advise to keep them as an IntProperty instead of a socket, just to keep this logic intact).
You could check some of my nodes (they are for cycles, but the logic is basically the same for the compositor).
All you need is to use a CompositorNodeTree instead of the ShaderNodeTree I use. Then add the size property to the node, with an update function to change the inside blur node values. In the end, you only need to expose those properties in the draw_buttons() function.
I think there might be unforeseen uses for any input. Unless there is a specific technical reason for not having an input exposed as a socket, if a value is possible to input by hand it should also take an input in form of a socket. The uses might not be apparent at first. Whoever programmed Vector Mapping node for Cycles must have thought at the time it did not make sense to have all the values as sockets - a terrible mistake! It is extremely useful to have those inputs as sockets. Luckily they can be easily made with math nodes.
As for adding them with python - that’s just awesome! I will have to try that as well. Thanks! 
