def extract_labels(filename):
    """Extract the labels into a 1D uint8 numpy array [index]."""
    with gzip.open(filename) as bytestream:
        magic = _read32(bytestream)
        if magic != 2049:
            raise ValueError(
                'Invalid magic number %d in MNIST label file: %s' %
                (magic, filename))
        num_items = _read32(bytestream)
        buf = bytestream.read(num_items)
        labels = numpy.frombuffer(buf, dtype=numpy.uint8)
        return labels
Extract the labels into a 1D uint8 numpy array [index].
tensorpack/dataflow/dataset/mnist.py