Loops through all materials and if it has a VRay material ID it prints the material name, the ID and if selectMaterial is set to True it selects the materials.

VrayID.py

import pymel.core as pm
import pymel.core.general


# select materials
allMat = pm.ls(materials=True)
vrayID = {}
selectMaterial = True

for mat in allMat:
    
    # get the sg
    sg = mat.listConnections(type='shadingEngine')[0]
    
    # check if the vray material ID attr exists
    try: 
        pymel.core.general.PyNode(sg+'.vrayMaterialId')
        vrayID.update({sg: sg.vrayMaterialId.get()})
            
    except AttributeError, error:
        pass
        #print(error)

for sg in vrayID:
    # get the connected material
    mat = pm.listConnections(sg, d=False, s=True)
    id = vrayID.get(sg)
    print(mat[0] + 'ID:   %s' %id)
    
    if(selectMaterial):
        pm.select(mat, add=True)