WIP: Add API tests for metadata handling #107
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| f = from_source("file", earthkit_examples_file("test_single.grib")) | ||
| md = f[0].metadata() | ||
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| assert isinstance(md, GribMetadata) |
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Do you suggest only to change the behaviour of GribField.metadata() when called without arguments, so, the rest of the functionality would be kept?
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Yes, that was the idea. We keep the current API, but change the underlying metadata object, and we return it if the user is not asking for specific keys/namespaces
| assert md.get("shortName") == "2t" | ||
| with pytest.raises(KeyError): | ||
| md["nonExistentKey"] | ||
| assert md.get("nonExistentKey", 12) == 12 |
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What should happen for:
md.get("nonExistentKey")Should we raise KeyError or return None as a dict would do?
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I would return None, to match dict and the behaviour of the default value when given
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Thank you @oiffrig! There is another question related to the type cast. On a Field we can call metadata() like this to specify the value type we want:
f.metadata("centre", astype=str)
f.metadata("centre", astype=int)
f.metadata("centre:s")
f.metadata("centre:str")
f.metadata("centre:l")
f.metadata("centre:int")How would the Metadata object support these? The last 4 calls are of course supported for GRIB by [] and get().
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Not totally sure. What I would suggest is to have that as an overridable behaviour: the metadata object knows a few types and can convert from them (raising an error if the type is not supported), and specific implementations (e.g. GRIB) can extend the default behaviour by using functionalities of the underlying backend
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Thanks. Would that mean that get should work like that:
md.get("centre", astype=int)
A concrete example on how we could handle metadata. Still work in progress and open for discussion.