Duvida

from pprint import pprint

lista_original = [25, 22, 17, 17, 18, 18, 16, 27, 24, 24, 19, 20, 28, 28, 23, 26, 30, 29, 31, 21]
nova_lista=[]

for tripla in zip(lista_original[:-1],lista_original[1:],lista_original[2:]):
    if len(tripla) == len(set(tripla)):
        if len(nova_lista)>0:
            if nova_lista[-1][-1]!=tripla[0]:
                nova_lista.append(tripla)
        else:
            nova_lista.append(tripla)
                

pprint(nova_lista) 
        
"""
[(25, 22, 17)    25 22 17
(18, 16, 27)     18 16 27     
(16, 27, 24)     16 27 24
(19, 20, 28)     19 20 28
(23, 26, 30)     23 26 30
(26, 30, 29)     26 30 29
(30, 29, 31)     30 29 31
(29, 31, 21)]    29 31 21
"""