MtoA provides an arnoldFlushCache command (and the Arnold > Flush Caches menu uses that command). You can call it from Python like this:
import maya.cmds as cmds cmds.arnoldFlushCache( textures=True )
Here’s a question asked recently. Given a shading tree like the one below, why don’t AOVs like diffuse_direct include the blended color from the Blend Color node?
The answer: because it is the Standard shader that writes the AOV, not the Blend Color shader. The diffuse_direct AOV gets the diffuse layer calculated by the Standard shader, and that’s it.
The MtoA AOV browser shows you what AOVs are implemented by which shaders:
Arnold Support Corner 