Merge pull request #58 from ecmwf/issue54-filter

Fix #54. Do not lose or mix variables when cfVarName or shortName are not unique

README.rst

@@ -386,6 +386,13 @@ Data variables:
     orog        (y, x) float32 ...
     tp          (y, x) float32 ...
     acpcp       (y, x) float32 ...
+    csnow       (y, x) float32 ...
+    cicep       (y, x) float32 ...
+    cfrzr       (y, x) float32 ...
+    crain       (y, x) float32 ...
+    cape        (y, x) float32 ...
+    cin         (y, x) float32 ...
+    hpbl        (y, x) float32 ...
 Attributes:
     GRIB_edition:            2
     GRIB_centre:             kwbc
@@ -500,6 +507,46 @@ Attributes:
     Conventions:             CF-1.7
     institution:             US National Weather Service - NCEP...
     history:                 ..., <xarray.Dataset>
+Dimensions:                 (heightAboveGroundLayer: 2, x: 93, y: 65)
+Coordinates:
+    time                    datetime64[ns] ...
+    step                    timedelta64[ns] ...
+  * heightAboveGroundLayer  (heightAboveGroundLayer) int64 1000 3000
+    latitude                (y, x) float64 ...
+    longitude               (y, x) float64 ...
+    valid_time              datetime64[ns] ...
+Dimensions without coordinates: x, y
+Data variables:
+    hlcy                    (heightAboveGroundLayer, y, x) float32 ...
+Attributes:
+    GRIB_edition:            2
+    GRIB_centre:             kwbc
+    GRIB_centreDescription:  US National Weather Service - NCEP...
+    GRIB_subCentre:          0
+    Conventions:             CF-1.7
+    institution:             US National Weather Service - NCEP...
+    history:                 ..., <xarray.Dataset>
+Dimensions:     (x: 93, y: 65)
+Coordinates:
+    time        datetime64[ns] ...
+    step        timedelta64[ns] ...
+    tropopause  int64 ...
+    latitude    (y, x) float64 ...
+    longitude   (y, x) float64 ...
+    valid_time  datetime64[ns] ...
+Dimensions without coordinates: x, y
+Data variables:
+    pres        (y, x) float32 ...
+    t           (y, x) float32 ...
+    u           (y, x) float32 ...
+Attributes:
+    GRIB_edition:            2
+    GRIB_centre:             kwbc
+    GRIB_centreDescription:  US National Weather Service - NCEP...
+    GRIB_subCentre:          0
+    Conventions:             CF-1.7
+    institution:             US National Weather Service - NCEP...
+    history:                 ..., <xarray.Dataset>
 Dimensions:     (x: 93, y: 65)
 Coordinates:
     time        datetime64[ns] ...

cfgrib/dataset.py

@@ -436,11 +436,13 @@ def build_dataset_components(
 ):
     filter_by_keys = dict(filter_by_keys)
     index = stream.index(ALL_KEYS, indexpath=indexpath).subindex(filter_by_keys)
-    param_ids = index['paramId']
     dimensions = collections.OrderedDict()
     variables = collections.OrderedDict()
-    for param_id, short_name, var_name in zip(param_ids, index['shortName'], index['cfVarName']):
+    for param_id in index['paramId']:
         var_index = index.subindex(paramId=param_id)
+        first = var_index.first()
+        short_name = first['shortName']
+        var_name = first['cfVarName']
         try:
             dims, data_var, coord_vars = build_variable_components(
                 var_index, encode_cf, filter_by_keys, errors=errors,