Raise ValueError upon attempt to create data-less Data
#491
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| # case of 'default' Data i.e. if no parameters are specified. | ||
| cf.Data(0, "s") | ||
| cf.Data(array=np.arange(5)) | ||
| cf.Data(source=self.filename) |
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An interesting choice of source (i.e. a string), but it certainly proves the test :)
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Oh, I didn't realise this was an abnormal usage! What is a source argument meant to be, precisely (a file handle or similar I am guessing based on a quick look at some other usage across the codebase?). It's not actually documented (specifically, no type given or indicated) right now:
Lines 300 to 304 in d9d34be
so maybe we can update that docstring description now in this PR?
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Hi Sadie, source can be anything that sufficiently duck types to the class of the object being instantiated. "Sufficiently" meaning that it'll take what it can and ignore what it can't, hence setting it to a string doesn't fail - it just doesn't provide much content (strings don't have dask arrays, etc.). It very commonly used in copy methods, which set source=self.
All cfdm and cf-python classes have a source parameter (because they all inherit from cfdm.core.Container, which has one), so we should perhaps consider improving this docstring in another PR ...
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Thanks for clarifying David. That all makes sense.
... so we should perhaps consider improving this docstring in another PR ...
Good idea. I'll raise an Issue linking to this thread, update the line in question to specify something normal and sensible for the source parameter, and merge the PR.
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(One of the CI jobs has failed due to multiple |
Closes #378.