Function _eagerly_encode_cf_timedelta

xarray/coding/times.py:1255–1314

(
    timedeltas: T_DuckArray,  # type: ignore[misc]
    units: str | None = None,
    dtype: np.dtype | None = None,
    allow_units_modification: bool = True,
)

def _eagerly_encode_cf_timedelta(
    timedeltas: T_DuckArray,  # type: ignore[misc]
    units: str | None = None,
    dtype: np.dtype | None = None,
    allow_units_modification: bool = True,
) -> tuple[T_DuckArray, str]:
    data_units = infer_timedelta_units(timedeltas)
    if units is None:
        units = data_units
    # units take precedence in the case of zero-size array
    if timedeltas.size == 0:
        data_units = units

    time_delta = _unit_timedelta_numpy(units)
    time_deltas = pd.TimedeltaIndex(ravel(timedeltas))
    # get resolution of TimedeltaIndex and align time_delta
    deltas_unit = time_deltas.unit
    time_delta = time_delta.astype(f"=m8[{deltas_unit}]")

    # retrieve needed units to faithfully encode to int64
    needed_units = data_units
    if data_units != units:
        needed_units = _infer_time_units_from_diff(np.unique(time_deltas.dropna()))

    # needed time delta to encode faithfully to int64
    needed_time_delta = _unit_timedelta_numpy(needed_units)

    floor_division = np.issubdtype(dtype, np.integer) or dtype is None
    if time_delta > needed_time_delta:
        floor_division = False
        if dtype is None:
            emit_user_level_warning(
                f"Timedeltas can't be serialized faithfully to int64 with requested units {units!r}. "
                f"Resolution of {needed_units!r} needed. Serializing timeseries to floating point instead. "
                f"Set encoding['dtype'] to integer dtype to serialize to int64. "
                f"Set encoding['dtype'] to floating point dtype to silence this warning."
            )
        elif np.issubdtype(dtype, np.integer) and allow_units_modification:
            emit_user_level_warning(
                f"Timedeltas can't be serialized faithfully with requested units {units!r}. "
                f"Serializing with units {needed_units!r} instead. "
                f"Set encoding['dtype'] to floating point dtype to serialize with units {units!r}. "
                f"Set encoding['units'] to {needed_units!r} to silence this warning ."
            )
            units = needed_units
            time_delta = needed_time_delta
            time_delta = time_delta.astype(f"=m8[{deltas_unit}]")
            floor_division = True
        elif np.issubdtype(dtype, np.integer) and not allow_units_modification:
            raise ValueError(
                f"Timedeltas can't be serialized faithfully to int64 with requested units {units!r}. "
                f"Consider setting encoding['dtype'] to a floating point dtype to serialize with "
                f"units {units!r}. Consider setting encoding['units'] to {needed_units!r} to "
                f"serialize with an integer dtype."
            )

    num = _division(time_deltas, time_delta, floor_division)
    num = reshape(num.values, timedeltas.shape)