Вот что вы можете сделать:
l1 = [1,2,3,4]
l2 = [3,5,6,1,2,3,4,6]
found = False
for i in range(len(l2)-len(l1)+1):
if l2[i:i+len(l1)] == l1:
found = True
if found:
print('found')
else:
print('not found')
Вывод:
found
Другой способ:
l1 = [1,2,3,4]
l2 = [3,5,6,1,2,3,4,6]
if str(l1)[1:-1] in str(l2)[1:-1]:
print('found')
else:
print('not found')
Вывод:
found