Womas and Blackheads are different species.
Womas are Aspidites ramsayi, whereas Blackheads are Aspidites melanocephalus.
Correct me if I'm wrong, but I believe these are the only two species within the genus Aspidites, which is characterized by lacking the labial (lower lip) heat-sensing pits.
The two species can easily be identified by the characteristic black head of Aspidites melanocephalus, as the common name (Blackheaded Python) and species name (melano = black, cephal = head, ie black head) suggest.
Womas lack this black head, but tend to have darker markings just dorsal to the eyes (just above the eyes).
The body patterns do tend to be somewhat similar between the two species however.