x = np.array([-1, 1, 2, 3, 4, 5, 7, -1, 4, 4, 4, 5, 6, 7, 7, 8, -1, 0, 2, 3,
    5, -1])
arrays = np.split(x, np.where(x == -1)[0])
arrays = [item[1:] for item in arrays if len(item) > 1]
Extract subarray between certain value in Python