ungridded_netcdf.py

"""
A plugin for reading ungridded (and CF-uncompliant) NetCDF files
"""
from cis.data_io.products import AProduct
import logging


class ungridded_netcdf(AProduct):

    def get_file_signature(self):
        return [r'.*\.nc']

    def create_coords(self, filenames, usr_variable=None):
        from cis.data_io.netcdf import read_many_files_individually, get_metadata, get_netcdf_file_variables
        from cis.data_io.Coord import Coord, CoordList
        from cis.data_io.ungridded_data import UngriddedCoordinates, UngriddedData
        from cis.exceptions import InvalidVariableError

        # We have to read it once first to find out which variables are in there. We assume the set of coordinates in
        # all the files are the same
        file_variables = get_netcdf_file_variables(filenames[0])

        def get_axis_std_name(var):
            axis=None
            lvar = var.lower()
            if lvar.startswith('lon'):
                axis = 'x', 'longitude'
            if lvar.startswith('lat'):
                axis = 'y', 'latitude'
            if lvar == 'G_ALT' or lvar == 'altitude' or lvar == 'pressure_altitude':
                axis = 'z', 'altitude'
            if lvar == 'time':
                axis = 't', 'time'
            if lvar == 'p' or lvar == 'pressure' or lvar == 'static_pressure':
                axis = 'p', 'air_pressure'
            return axis

        all_coord_variables = [(v, get_axis_std_name(v)) for v in file_variables if get_axis_std_name(v) is not None]
        # Get rid of any duplicates
        coord_variables = []
        for v in all_coord_variables:
            if v is None or v[1][1] not in [x[1][1] for x in coord_variables]:
                coord_variables.append(v)

        all_variables = coord_variables.copy()
        if usr_variable is not None:
            all_variables.append((usr_variable, ''))

        logging.info("Listing coordinates: " + str(all_variables))

        coords = CoordList()
        var_data = read_many_files_individually(filenames, [v[0] for v in all_variables])
        for name, axis_std_name in coord_variables:
            try:
                meta = get_metadata(var_data[name][0])
                if meta.standard_name is None:
                    meta.standard_name = axis_std_name[1]
                coord = Coord(var_data[name], meta, axis=axis_std_name[0])
                if meta.standard_name == 'time':
                    # Remove the mask from the time coordinate since this screws up date conversion...
                    coord.data = coord.data.data
                    # Converting units to CIS std time
                    coord.convert_to_std_time()
                coords.append(coord)
            except InvalidVariableError:
                pass

        if usr_variable is None:
            res = UngriddedCoordinates(coords)
        else:
            res = UngriddedData(var_data[usr_variable], get_metadata(var_data[usr_variable][0]), coords)

        return res

    def create_data_object(self, filenames, variable):
        return self.create_coords(filenames, variable)