imos_template.py

from datetime import datetime
from pkg_resources import resource_filename

from netCDF4 import num2date

from .template import DatasetTemplate

IMOS_GLOBAL_JSON = resource_filename(__name__, "imos_global.json")
IMOS_GLOBAL_ATTRIBUTES = DatasetTemplate.from_json(IMOS_GLOBAL_JSON).global_attributes

TIMESTAMP_FORMAT = "%Y-%m-%dT%H:%M:%SZ"


class ImosTemplate(DatasetTemplate):
    """Template class to create IMOS-compliant netCDF files"""

    def __init__(self, global_attributes=None, *args, **kwargs):
        # add standard IMOS global attributes first
        combined_attributes = IMOS_GLOBAL_ATTRIBUTES.copy()
        if global_attributes is not None:
            combined_attributes.update(global_attributes)
        super(ImosTemplate, self).__init__(
            global_attributes=combined_attributes, *args, **kwargs
        )
        self._date_created = None

    @property
    def date_created(self):
        """Read-only property to return the UTC creation time of the netCDF file as a datetime object"""
        if self._date_created is None:
            self._date_created = datetime.utcnow()
        return self._date_created

    def add_date_created_attribute(self):
        self.global_attributes["date_created"] = self.date_created.strftime(
            TIMESTAMP_FORMAT
        )

    def add_extent_attributes(
        self, time_var="TIME", vert_var="DEPTH", lat_var="LATITUDE", lon_var="LONGITUDE"
    ):
        """
        Calculate spatial and temporal extents from coordinate variables in the template and add/update
        the relevant global attributes. Set an input variable name to None to skip that coordinate.

        :param time_var: Name of the time variable to use (default 'TIME')
        :param vert_var: Name of the vertical coordinate variable (default 'DEPTH')
        :param lat_var: Name of the latitude variable (default 'LATITUDE')
        :param lon_var: Name of the longitude variable (default 'LONGITUDE')
        :return: None
        """
        if time_var:
            data_range = self.get_data_range(time_var)
            time = self.variables[time_var]
            units = time.get("units")
            if not units:
                raise ValueError(
                    "Time variable '{time_var}' has no units".format(time_var=time_var)
                )
            calendar = time.get("calendar", "gregorian")
            time_range = num2date(data_range, units, calendar)
            self.global_attributes["time_coverage_start"] = time_range[0].strftime(
                TIMESTAMP_FORMAT
            )
            self.global_attributes["time_coverage_end"] = time_range[1].strftime(
                TIMESTAMP_FORMAT
            )

        if vert_var:
            vmin, vmax = self.get_data_range(vert_var)
            self.global_attributes["geospatial_vertical_min"] = vmin
            self.global_attributes["geospatial_vertical_max"] = vmax

        if lat_var:
            vmin, vmax = self.get_data_range(lat_var)
            self.global_attributes["geospatial_lat_min"] = vmin
            self.global_attributes["geospatial_lat_max"] = vmax

        if lon_var:
            vmin, vmax = self.get_data_range(lon_var)
            self.global_attributes["geospatial_lon_min"] = vmin
            self.global_attributes["geospatial_lon_max"] = vmax

    # TODO: def set_imos_filename(self):