Transfer blendshape between mesh with different topology. In this case from head to additional meshes (eyebrows, moustache, etc)

FaceAttachmentAutoBlendshape.py

import maya.cmds as cmds

blendshapeList = []
# TODO: Change this, hard code for now
objectAffected = "eyebrow"
mainHead = None
blendshapeCopies = []
meshDeformer = None
renamedBlendshapesArray = []

# Get blendshapes of head
def GetHeadBlendshapes():
    global blendshapeList
    global mainHead
    global meshDeformer
    selectedObjects = cmds.ls(selection=True)
    # List all deformers applied to the selected object
    for selectedObject in selectedObjects:
        # TODO: Add better check on this. Set selected object as baseMesh
        mainHead = selectedObject
        meshName = mainHead.split('|')[-1]
        meshDeformer = cmds.listHistory(mainHead)
        for deformer in meshDeformer:
            if cmds.nodeType(deformer) == "blendShape":
                blendShape = cmds.blendShape(deformer, q=True, target=True)
                blendshapeTargets = cmds.listAttr(deformer + '.weight', multi=True)
                for b in blendshapeTargets:
                    print(b)
                    if b not in blendshapeList:
                        blendshapeList.append(b)

# Create copies of original eyebrow, based on number of blendshapes
def MakeCopiesFacialObject():
    global blendshapeCopies
    # TODO: Change this later, currently selecting by name
    facialObject = cmds.ls(objectAffected)
    for b in blendshapeList:
        blendshapeDuplicate = cmds.duplicate(facialObject, returnRootsOnly=True)
        blendshapeCopies.append(blendshapeDuplicate)

# Wrap modifier on each eyebrow copies
def WrapEyebrowCopy():
    for bc in blendshapeCopies:
        AddWrapDeformer(bc, mainHead)
        '''       
        wrapDeformer = cmds.deformer(bc, type='wrap')[0]
        # Set source mesh, in this case the head
        cmds.setAttr(wrapDeformer + '.maxDistance', 1.0)
        cmds.setAttr(wrapDeformer + '.autoWeightThreshold', 1.0)
        #cmds.setAttr(wrapDeformer + '.weightThreshold', 1.0)
        # Connect this deformer
        cmds.connectAttr(str(mainHead) + '.worldMesh[0]', wrapDeformer + '.driverPoints[0]')
        #AddWrapDeformer(bc, mainHead)
        '''

def AddWrapDeformer(targetMesh, driverMesh):
    '''
    wrapNode = cmds.deformer(targetMesh, type='wrap')[0]
    cmds.setAttr(wrapNode + '.driver[0]', driverMesh, type='string')
    '''
    cmds.select(targetMesh)
    cmds.select(driverMesh, add=True)
    cmds.CreateWrap()
    cmds.select(clear=True)

def RenameBlendshapeCopies():
    # Name the copies to be the same with blendshape name    
    for i, copy in enumerate(blendshapeCopies):
        newBS = cmds.rename(copy, blendshapeList[i])
        renamedBlendshapesArray.append(newBS)

# For loop on each blendshape, set it to 1 on each
# Freeze transform on each eyebrow deformed by each blendshape
def UpdateBlendshapeCopy():
    for i, copy in enumerate(blendshapeCopies):
        print("THISISTHECOPY")
        print(copy)
        for md in meshDeformer:
            if cmds.nodeType(md) == "blendShape":
                print(md)
                blendShape = cmds.listAttr(md + '.weight', multi=True)
                for b in blendShape:
                    bShape = cmds.listRelatives(b, shapes=True)                     
                    # TODO: Somehow there's Shape appended to the name of these blendshape, need to remove them. This is also not great
                    bShape = str(bShape[0])[:-5]
                    if blendshapeList[i] == bShape:
                        cmds.setAttr((str(md) + "." + str(bShape)), 1)
                        print ("PROCESSINGNOW")
                        print(blendshapeList[i])
                        print(bShape)
                        print(renamedBlendshapesArray[i])
                    # Set all other blendshapes to 0                    
                    else:
                        cmds.setAttr((str(md) + "." + str(bShape)), 0)
                cmds.select(clear=True)
                cmds.select(renamedBlendshapesArray[i])
                cmds.delete(renamedBlendshapesArray[i], constructionHistory=True)
                cmds.select(clear=True)

# TODO: Create blendshapes on original eyebrow, picking the deformed eyebrow
def MakeBlendshapes():
    print("Making blendshapes")

def RunThis():
    GetHeadBlendshapes()
    MakeCopiesFacialObject()
    WrapEyebrowCopy()
    RenameBlendshapeCopies()
    UpdateBlendshapeCopy()    

RunThis()