def updateFeature(font, name, value):
 featureRE = compileFeatureRE(name)
 if featureRE.search(font.features.text):
  font.features.text = featureRE.sub(value, font.features.text)
 else:
  font.features.text += ('\n' + value)

def updateFeature ( font , name , value ) : featureRE = compileFeatureRE ( name ) if featureRE . search ( font . features . text ) : font . features . text = featureRE . sub ( value , font . features . text ) else : font . features . text += ( '\n' + value )
add a feature definition .