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from __future__ import annotations
import os
import warnings
import numpy as np
from xarray.backends.common import (
BACKEND_ENTRYPOINTS,
AbstractDataStore,
BackendArray,
BackendEntrypoint,
_normalize_path,
)
from xarray.backends.locks import SerializableLock, ensure_lock
from xarray.backends.store import StoreBackendEntrypoint
from xarray.core import indexing
from xarray.core.utils import Frozen, FrozenDict, close_on_error, module_available
from xarray.core.variable import Variable
# FIXME: Add a dedicated lock, even if ecCodes is supposed to be thread-safe
# in most circumstances. See:
# https://confluence.ecmwf.int/display/ECC/Frequently+Asked+Questions
ECCODES_LOCK = SerializableLock()
class CfGribArrayWrapper(BackendArray):
def __init__(self, datastore, array):
self.datastore = datastore
self.shape = array.shape
self.dtype = array.dtype
self.array = array
def __getitem__(self, key):
return indexing.explicit_indexing_adapter(
key, self.shape, indexing.IndexingSupport.BASIC, self._getitem
)
def _getitem(self, key):
with self.datastore.lock:
return self.array[key]
class CfGribDataStore(AbstractDataStore):
"""
Implements the ``xr.AbstractDataStore`` read-only API for a GRIB file.
"""
def __init__(self, filename, lock=None, **backend_kwargs):
try:
import cfgrib
# cfgrib throws a RuntimeError if eccodes is not installed
except (ImportError, RuntimeError) as err:
warnings.warn(
"Failed to load cfgrib - most likely there is a problem accessing the ecCodes library. "
"Try `import cfgrib` to get the full error message"
)
raise err
if lock is None:
lock = ECCODES_LOCK
self.lock = ensure_lock(lock)
self.ds = cfgrib.open_file(filename, **backend_kwargs)
def open_store_variable(self, name, var):
if isinstance(var.data, np.ndarray):
data = var.data
else:
wrapped_array = CfGribArrayWrapper(self, var.data)
data = indexing.LazilyIndexedArray(wrapped_array)
encoding = self.ds.encoding.copy()
encoding["original_shape"] = var.data.shape
return Variable(var.dimensions, data, var.attributes, encoding)
def get_variables(self):
return FrozenDict(
(k, self.open_store_variable(k, v)) for k, v in self.ds.variables.items()
)
def get_attrs(self):
return Frozen(self.ds.attributes)
def get_dimensions(self):
return Frozen(self.ds.dimensions)
def get_encoding(self):
dims = self.get_dimensions()
return {"unlimited_dims": {k for k, v in dims.items() if v is None}}
class CfgribfBackendEntrypoint(BackendEntrypoint):
available = module_available("cfgrib")
def guess_can_open(self, filename_or_obj):
try:
_, ext = os.path.splitext(filename_or_obj)
except TypeError:
return False
return ext in {".grib", ".grib2", ".grb", ".grb2"}
def open_dataset(
self,
filename_or_obj,
*,
mask_and_scale=True,
decode_times=True,
concat_characters=True,
decode_coords=True,
drop_variables=None,
use_cftime=None,
decode_timedelta=None,
lock=None,
indexpath="{path}.{short_hash}.idx",
filter_by_keys={},
read_keys=[],
encode_cf=("parameter", "time", "geography", "vertical"),
squeeze=True,
time_dims=("time", "step"),
):
filename_or_obj = _normalize_path(filename_or_obj)
store = CfGribDataStore(
filename_or_obj,
indexpath=indexpath,
filter_by_keys=filter_by_keys,
read_keys=read_keys,
encode_cf=encode_cf,
squeeze=squeeze,
time_dims=time_dims,
lock=lock,
)
store_entrypoint = StoreBackendEntrypoint()
with close_on_error(store):
ds = store_entrypoint.open_dataset(
store,
mask_and_scale=mask_and_scale,
decode_times=decode_times,
concat_characters=concat_characters,
decode_coords=decode_coords,
drop_variables=drop_variables,
use_cftime=use_cftime,
decode_timedelta=decode_timedelta,
)
return ds
BACKEND_ENTRYPOINTS["cfgrib"] = CfgribfBackendEntrypoint
|
