You might need to check out numpy.flatten and numpy.ravel, both return a 1-d array from an n-d array.

Furthermore, if you're not going to modify the returned 1-d array, I suggest you use numpy.ravel, since it doesn't make a copy of the array, but just return a view of the array, which is much faster than numpy.flatten.

>>>a = np.arange(10000).reshape((100,100))

>>>%timeit a.flatten()
100000 loops, best of 3: 4.02 µs per loop

>>>%timeit a.ravel()
1000000 loops, best of 3: 412 ns per loop

Also check out this post.

You can write a recursive function in order to flatten the list.

def flatten(permutations):
    flattens = []
    for permutation in permutations:
        if len(permutation) == 2:
            flattens.extend([[permutation[0], *j] for j in flatten(permutation[1])])

        else:
            flattens.extend(permutation)

    return flattens


if __name__ == '__main__':
    permutations = [['a', [['b', ['c']], ['c', ['b']]]], ['b', [['a', ['c']], ['c', ['a']]]], ['c', [['a', ['b']], ['b', ['a']]]]]
    print(flatten(permutations))

Output:

[['a', 'b', 'c'], ['a', 'c', 'b'], ['b', 'a', 'c'], ['b', 'c', 'a'], ['c', 'a', 'b'], ['c', 'b', 'a']]