A super janky example of how _repr_html_ could be implemented

pprint_numpy.py

import numpy as np

def _html_repr_helper(contents, index=()):
    dims_left = contents.ndim - len(index)
    if dims_left == 0:
        s = contents[index]
    else:
        s = ''.join(_html_repr_helper(contents, index + (i,)) for i in range(contents.shape[len(index)]))

    return "<div class='numpy-array-ndim-{} numpy-array-ndim-m{}' title='[{}]'>{}</div>".format(
        len(index), dims_left,
        ','.join('{}'.format(i) for i in (index + (':',) * dims_left)),
        s,
    )

class Pretty(np.ndarray):
    def _repr_html_(self):
        css = """
        .numpy-array {
            display: inline-block;
        }
        .numpy-array div {
            border: 1px solid black;
            margin: 2px;
            display: flex;
            flex-direction: column;
            flex: 1 1 auto;
        }
        .numpy-array div:hover {
            border: 1px solid red;
        }
        .numpy-array div.numpy-array-ndim-m1 {
            flex-direction: row;
        }
        .numpy-array div.numpy-array-ndim-m0 {
            padding: 5px;
        }
        """
        return """<div class='numpy-array'><style>{}</style>{}</div>""".format(css, _html_repr_helper(self))
      
def make_pretty(x):
    return np.asarray(x).view(Pretty)