Python. Compute keypoints and descriptor with multiple images

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I'm trying to compute keypoints and descriptors for a given set of images with cv2.xfeatures2d.SIFT. I want to create an array with all keypoints from every images and another array for descriptors too:

kp = numpy.empty([]) 
dsc = numpy.empty([])
        for imagesFiles in range(0, len(imagesCoast)):
        sift = cv2.xfeatures2d.SIFT_create()
        kp[imagesFiles], dsc[imagesFiles] = sift.detectAndCompute(imagesCoast[imagesFiles], None)

When I run it, output says:

keypts[imagesFiles], descriptor[imagesFiles] = `sift.detectAndCompute(imagesCoast[imagesFiles], None)`IndexError: 0-d arrays can't be indexed

What I'm doing wrong? If I delete [imagesFiles] from kp and dsc it computes everything for each imagesFiles, but them only keeps keypoits and descriptor for last one? I would like to know also, what does mean IndexError: 0-d arrays

Thanks in advance José Soto