ValueError: key present and new value is different...

@darrenleeweber has reported on #2 a problem that deserves it’s own issue:

Thanks, also bumped into this while trying to read a GFS grib2 file, e.g.

import cfgrib
ds = cfgrib.Dataset.frompath('gfs_4_20110807_0000_000.grb2')
# snipped traceback
~/anaconda3/lib/python3.6/site-packages/cfgrib/dataset.py in enforce_unique_attributes(index, attributes_keys)
    113         values = index[key]
    114         if len(values) > 1:
--> 115             raise ValueError("multiple values for unique attribute %r: %r" % (key, values))
    116         if values and values[0] not in ('undef', 'unknown'):
    117             attributes['GRIB_' + key] = values[0]

ValueError: multiple values for unique attribute 'typeOfLevel': ['isobaricInhPa', 'tropopause', 'maxWind', 'isothermZero', 'unknown', 'potentialVorticity']

The work around seems to work, but hits another snag for this particular data example, i.e.

ds = cfgrib.Dataset.frompath('gfs_4_20110807_0000_000.grb2', filter_by_keys={'typeOfLevel': 'isobaricInhPa'})
# snipped traceback
~/anaconda3/lib/python3.6/site-packages/cfgrib/dataset.py in build_dataset_components(stream, encode_parameter, encode_time, encode_vertical, encode_geography, filter_by_keys)
    374         vars = collections.OrderedDict([(short_name, data_var)])
    375         vars.update(coord_vars)
--> 376         dict_merge(dimensions, dims)
    377         dict_merge(variables, vars)
    378     attributes = enforce_unique_attributes(index, GLOBAL_ATTRIBUTES_KEYS)

~/anaconda3/lib/python3.6/site-packages/cfgrib/dataset.py in dict_merge(master, update)
    353         else:
    354             raise ValueError("key present and new value is different: "
--> 355                              "key=%r value=%r new_value=%r" % (key, master[key], value))
    356 
    357 

ValueError: key present and new value is different: key='air_pressure' value=26 new_value=25

It’s not easy to figure out if this is cfgrib or the data is not conforming.

[alexamici]

Raising or ignoring the exception is now configurable via the errors option in backend_kwargs. The default is strict that keep the exception but can be set to ignore to just drop the offending hypecubes.

[alexamici]

It worked this time (FYI I added --no-sign-request), you can take the file down. Thanks!