Blender material preview in node editor

material_preview.py

import bpy


class PreviewPanel(bpy.types.Panel):
	bl_label = "Material preview"
	bl_space_type = "NODE_EDITOR"
	bl_region_type = "UI"

	@classmethod
	def poll(cls, context):
		return context.active_object is not None and context.object.active_material is not None

	def draw(self, context):
		ob = context.active_object
		self.layout.template_ID_preview(ob, "active_material")
		#self.layout.template_preview(ob.active_material)


def register():
	bpy.utils.register_class(PreviewPanel)


def unregister():
	bpy.utils.unregister_class(PreviewPanel)


if __name__ == "__main__":
	register()