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# pylint: disable=invalid-name, line-too-long, unused-variable, too-many-locals
"""Space to depth in python"""

import numpy as np


def space_to_depth_python(data, block_size):
    """Space to Depth operator in python for NCHW layout.

    Parameters
    ----------
    data : np.ndarray
        4-D with shape [batch, in_channel, in_height, in_width]

    block_size : int
        Size of spatial blocks to decompose into channels.

    Returns
    -------
    d2s_out : np.ndarray
        4-D with shape [batch, in_channel * (block_size * block_size),
                        out_height / block_size, out_width / block_size]
    """
    in_n, in_c, in_h, in_w = data.shape
    new_h = int(in_h / block_size)
    new_w = int(in_h / block_size)
    new_c = int(in_c * (block_size * block_size))

    expanded = np.reshape(data, newshape=[in_n, in_c, new_h, block_size, new_w, block_size])
    transposed = np.transpose(expanded, axes=[0, 3, 5, 1, 2, 4])
    newshape = [in_n, new_c, new_h, new_w]
    d2s_out = np.reshape(transposed, newshape=newshape)
    return d2s_out
