I need to apply alignment to each face of the selected polygon on UV? But I absolutely do not understand how to work with UV through Python(.
It seems I have to cycle through to select all belonging to the polygon uv magnifier and align them, but what API for this. Very little is written about it on the Internet
This should help you out. 
Yes, but how do you select vertex, edge, face in uv editor? I just don’t understand or see