Class CFTimedeltaCoder

xarray/coding/times.py:1474–1559

Coder for CF Timedelta coding. Parameters ---------- time_unit : PDDatetimeUnitOptions Target resolution when decoding timedeltas via units. Defaults to "ns". When decoding via dtype, the resolution is specified in the dtype attribute, so this parameter is ignore

class CFTimedeltaCoder(VariableCoder):
    """Coder for CF Timedelta coding.

    Parameters
    ----------
    time_unit : PDDatetimeUnitOptions
        Target resolution when decoding timedeltas via units. Defaults to "ns".
        When decoding via dtype, the resolution is specified in the dtype
        attribute, so this parameter is ignored.
    decode_via_units : bool
        Whether to decode timedeltas based on the presence of a timedelta-like
        units attribute, e.g. "seconds". Defaults to True, but in the future
        will default to False.
    decode_via_dtype : bool
        Whether to decode timedeltas based on the presence of an np.timedelta64
        dtype attribute, e.g. "timedelta64[s]". Defaults to True.
    """

    def __init__(
        self,
        time_unit: PDDatetimeUnitOptions | None = None,
        decode_via_units: bool = False,
        decode_via_dtype: bool = True,
    ) -> None:
        self.time_unit = time_unit
        self.decode_via_units = decode_via_units
        self.decode_via_dtype = decode_via_dtype

    def encode(self, variable: Variable, name: T_Name = None) -> Variable:
        if np.issubdtype(variable.dtype, np.timedelta64):
            dims, data, attrs, encoding = unpack_for_encoding(variable)
            dtype = encoding.get("dtype", None)
            units = encoding.pop("units", None)

            # in the case of packed data we need to encode into
            # float first, the correct dtype will be established
            # via CFScaleOffsetCoder/CFMaskCoder
            if "add_offset" in encoding or "scale_factor" in encoding:
                dtype = data.dtype if data.dtype.kind == "f" else "float64"

            resolution, _ = np.datetime_data(variable.dtype)
            attrs_dtype = f"timedelta64[{resolution}]"
            safe_setitem(attrs, "dtype", attrs_dtype, name=name)

            data, units = encode_cf_timedelta(data, units, dtype)
            safe_setitem(attrs, "units", units, name=name)
            return Variable(dims, data, attrs, encoding, fastpath=True)
        else:
            return variable

    def decode(self, variable: Variable, name: T_Name = None) -> Variable:
        units = variable.attrs.get("units", None)
        has_timedelta_units = isinstance(units, str) and units in TIME_UNITS
        has_timedelta_dtype = has_timedelta64_encoding_dtype(variable.attrs)
        is_dtype_decodable = has_timedelta_units and has_timedelta_dtype
        is_units_decodable = has_timedelta_units
        if (is_dtype_decodable and self.decode_via_dtype) or (
            is_units_decodable and self.decode_via_units