Fetched_constraints is a class of argopy.utils.format.UriCName cannot directly save to netcdf

[cywhale]

Reproducible code:

ds = DataFetcher().float(5903377).to_xarray()
ds
ds.to_netcdf("./argo_data.nc")

Error message
File ~/.pyenv/versions/py312numpy1/lib/python3.12/site-packages/xarray/backends/api.py:1292, in to_netcdf(dataset, path_or_file, mode, format, group, engine, encoding, unlimited_dims, compute, multifile, invalid_netcdf)
1290 # validate Dataset keys, DataArray names, and attr keys/values
1291 _validate_dataset_names(dataset)
...
197 "netCDF files, its value must be of one of the following types: "
198 f"{', '.join([vtype.name for vtype in valid_types])}"
199 )

TypeError: Invalid value for attr 'Fetched_constraints': WMO5903377. For serialization to netCDF files, its value must be of one of the following types: str, Number, ndarray, number, list, tuple

Debugging:

for attr, value in ds.attrs.items():
    print(f"{attr}: {type(value)}")
    if not isinstance(value, (str, int, float, list, tuple, np.ndarray)):
        print(f"Converting {attr} to string")
        ds.attrs[attr] = str(value)  # Convert unsupported types to string

ds.to_netcdf("../tmp/argo_data.nc")

Fetched_constraints: <class 'argopy.utils.format.UriCName'>
Converting Fetched_constraints to string

and then save done

Problem Description

I think it come from
#400

ds.attrs["Fetched_constraints"] = UriCName(url).cname

Versions

Output of `argopy.show_versions()`

SYSTEM

commit: None
python: 3.12.5 (main, Sep 2 2024, 14:21:15) [GCC 13.2.0]
python-bits: 64
OS: Linux
OS-release: 6.8.0-45-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: None
LANG: zh_TW.UTF-8
LOCALE: zh_TW.UTF-8
libhdf5: 1.14.2
libnetcdf: 4.9.3-development

INSTALLED VERSIONS: CORE

aiohttp : 3.10.5
argopy : 1.0.0
decorator : 5.1.1
erddapy : 2.2.0
fsspec : 2023.10.0
netCDF4 : 1.7.1.post2
...

INSTALLED VERSIONS: PIP

[gmaze]

Hi @cywhale
thanks for raising a very well documented issue !

This bug indeed went under our radar and CI tests.

I'm fixing it right now in #413

[gmaze]

I think this is the origin:

The error was in

argopy/argopy/data_fetchers/erddap_data_processors.py

Line 79 in e2033a7

Fetched_constraints = UriCName(Fetched_url)

because later on we had:

argopy/argopy/data_fetchers/erddap_data_processors.py

Line 107 in e2033a7

this_ds.attrs["Fetched_constraints"] = Fetched_constraints

instead of Fetched_constraints.cname because the cname property is a string

[gmaze]

Seems to be working, I merged the fix to the main branch.
So this bug should be fixed in the next release.

In the mean time you can install argopy from the repo to benefit from the fix:

pip install git+http://github.com/euroargodev/argopy.git@master

[cywhale]

pip install git+http://github.com/euroargodev/argopy.git@master

Ya, confirmed it. Thanks for the quick revision.