hardsurface modelling script to set normals for all vertices on a face.

fixNormals.py

import pymel.core as pm

def faceNormal():
    """ """
    
    # Store old selection,
    selection = pm.selected()
    
    # Convert selection to faces,
    pm.mel.ConvertSelectionToFaces()
    
    # Iterate over each face in a flattened list of active selection,
    for face in pm.selected(flatten = True):
        
        # Get the face normal and list of vertices.
        normal = face.getNormal()
        
        pm.select(face)
        pm.mel.ConvertSelectionToVertices()

        # set their normal to normal of face.
        for vertex in pm.selected(flatten = True):
        
            # FIX: previously set normals will be overwritten by the latest operation,      
            pm.polyNormalPerVertex( vertex, xyz = normal )
            
    # Restore previous selection,
    pm.select(selection)
    
    
if __name__ == "__main__":       
    faceNormal()