def _prep_values(self, values=None, kill_inf=True, how=None):

        if values is None:
            values = getattr(self._selected_obj, 'values', self._selected_obj)

        # GH #12373 : rolling functions error on float32 data
        # make sure the data is coerced to float64
        if com.is_float_dtype(values.dtype):
            values = com._ensure_float64(values)
        elif com.is_integer_dtype(values.dtype):
            values = com._ensure_float64(values)
        elif com.needs_i8_conversion(values.dtype):
            raise NotImplementedError("ops for {action} for this "
                                      "dtype {dtype} are not "
                                      "implemented".format(
                                          action=self._window_type,
                                          dtype=values.dtype))
        else:
            try:
                values = com._ensure_float64(values)
            except (__HOLE__, TypeError):
                raise TypeError("cannot handle this type -> {0}"
                                "".format(values.dtype))

        if kill_inf:
            values = values.copy()
            values[np.isinf(values)] = np.NaN

        return values
dataset/ETHPy150Open pydata/pandas/pandas/core/window.py/_Window._prep_values