Попробуйте:
a = ['A', 'B', 'C']
for v in permutations(a):
for i in range(0, len(v), 2):
print v[i:i+2]
print '-'*10
Вывод:
('A', 'B')
('C',)
----------
('A', 'C')
('B',)
----------
('B', 'A')
('C',)
----------
('B', 'C')
('A',)
----------
('C', 'A')
('B',)
----------
('C', 'B')
('A',)
----------