PyMel function that copies the value(s) of the attribute from sourceObj to targetObj. Handles multi-attributes.

hlCopyAttr.py

import pymel.core as pm
sourceObj = pm.ls('aFluidShape')[0]
targetObj = pm.ls('myFluidShape')[0]

def hlCopyAttr(sourceObj, targetObj, attribute):
    """Copies the value(s) of the attribute from sourceObj to targetObj. Handles multi-attributes."""

    if pm.attributeQuery(attribute, node = targetObj.name(), exists=True): # Execute only if the entered attribute exists
        multiAttrCheck = pm.attributeQuery(attribute, node=targetObj.name(), m=1) # Check if it's a multi-attribute or not
        if multiAttrCheck: # If the attribute is a multi-attribute, copy the values from each instance
            extraInst = set(sourceObj.getAttr(attribute, mi=1)).symmetric_difference( set(targetObj.getAttr(attribute, mi=1)) ) # Get the set of extra instances in multi-attribute
            for ins in extraInst: # Remove these extra instances
                pm.removeMultiInstance('{0}.{1}[{2}]'.format(targetObj.name(), attribute, ins) )
            
            multiAttr = pm.attributeQuery(attribute, node=targetObj.name(), listChildren=1) # Get list of multi-attribute children
            for attrChild in multiAttr:
                for ind in sourceObj.getAttr(attribute, mi=1):
                    attrString = '{attr}[{index}].{child}'.format( attr = attribute,
                                                                   index = ind,
                                                                   child = attrChild )
                    
                    attrVal = sourceObj.getAttr( attrString )
                    targetObj.setAttr( attrString, attrVal )
                    print( '//  {objName}.{attr} was set to {val}  //'.format(objName = targetObj.name(),
                                                                      attr = attrString,
                                                                      val = attrVal) )
        else: # If not a multi-attribute, copy individual value
            attrVal = sourceObj.getAttr(attribute)
            targetObj.setAttr(attribute, attrVal)
            print('//  {0}.{1} was set to {2}  //\n'.format(targetObj.name(), attribute, attrVal) )
    else:
        print('!!  {0} does not exist  !!\n'.format(attribute))