Simple of numpy.busday_count that returns `float` arrays rather than int
    arrays, and handles `NaT`s by returning `NaN`s where the inputs were `NaT`.

    Doesn't support custom weekdays or calendars, but probably should in the
    future.

    See Also
    --------
    np.busday_count

def busday_count_mask_NaT(begindates, enddates, out=None):
    """
    Simple of numpy.busday_count that returns `float` arrays rather than int
    arrays, and handles `NaT`s by returning `NaN`s where the inputs were `NaT`.

    Doesn't support custom weekdays or calendars, but probably should in the
    future.

    See Also
    --------
    np.busday_count
    """
    if out is None:
        out = empty(broadcast(begindates, enddates).shape, dtype=float)

    beginmask = isnat(begindates)
    endmask = isnat(enddates)

    out = busday_count(
        # Temporarily fill in non-NaT values.
        where(beginmask, _notNaT, begindates),
        where(endmask, _notNaT, enddates),
        out=out,
    )

    # Fill in entries where either comparison was NaT with nan in the output.
    out[beginmask | endmask] = nan
    return out