Hey there!
1 - Is there a way to select uv faces from a specific region of the uv map?
For example i have uv island in uv region U:0-1 and V:1-2, and code should select those faces.
2 - Also a question, how can define in script if there is no uv faces in the investigated then selecting specifi uv region should stop?
I would like to make an automatic UDIM uv and material managing script, and this part would be crucial 
Thank You for the help in advance!