[[1][a]
 [2][b]
 [3][c]
 [4][d]]

[1,2,3,4],
[1,2,3,d],
[1,2,c,4],
[1,2,c,d],
[1,b,3,4],
[1,b,3,d],
[1,b,c,4],
[1,b,c,d],
...

a = [1,'a',
     2,'b',
     3,'c',
     4,'d']
b = []
for i in xrange(16):
	b.append([])
	for i, j in enumerate("%04d"%int(bin(x)[2:])) + bin(i)[2:]):
		b[-1].append(a[i*2+int(j)])
print b

a = [1,'a', 2,'b', 3,'c', 4,'d']
b = [[a[int(i*2+int(j))] for i, j in enumerate('0'*(4-len(bin(x)[2:])) + bin(x)[2:])] for x in xrange(16)]
print b

data = [['1', 'a'],
        ['2', 'b'],
        ['3', 'c'],
        ['4', 'd']]
def mkmask(n, w):
    return map(int, bin(n)[2:].zfill(w))
def domagic(data):
    w = len(data)
    for c in range(1 << w):
        m = mkmask(c, w)
        yield [p[m[i]] for i, p in enumerate(data)]
print(list(domagic(data)))