issues: 422903285

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
422903285 MDU6SXNzdWU0MjI5MDMyODU= 2822 to_netcdf() fails to write if input is read from netcdf3_classic 5186647 closed 0     6 2019-03-19T19:05:01Z 2023-12-15T20:48:05Z 2023-12-15T20:48:04Z NONE      

Code Sample

```python import xarray as xr with xr.open_dataset('some_netcdf_classic_file') as ds: data = ds #do something with data

Neither of these work, see exception below

data.to_netcdf('some_new_file', 'w') data.to_netcdf('some_new_file', 'a')

Writing back to the same file, or a new file with mode of NETCDF3_CLASSIC works

data.to_netcdf('some_netcdf_classic_file', 'a') data.to_netcdf('some_new_file', 'w', 'NETCDF3_CLASSIC') ```

Problem description

File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/core/dataset.py", line 1232, in to_netcdf compute=compute) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/api.py", line 747, in to_netcdf unlimited_dims=unlimited_dims) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/api.py", line 790, in dump_to_store unlimited_dims=unlimited_dims) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/common.py", line 263, in store self.set_attributes(attributes) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/common.py", line 279, in set_attributes self.set_attribute(k, v) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/netCDF4_.py", line 421, in set_attribute _set_nc_attribute(self.ds, key, value) File "/home/nels.frazier/.local/lib/python2.7/site-packages/xarray/backends/netCDF4_.py", line 297, in _set_nc_attribute obj.setncattr(key, value) File "netCDF4/_netCDF4.pyx", line 2619, in netCDF4._netCDF4.Dataset.setncattr File "netCDF4/_netCDF4.pyx", line 1479, in netCDF4._netCDF4._set_att File "netCDF4/_netCDF4.pyx", line 1745, in netCDF4._netCDF4._ensure_nc_success AttributeError: NetCDF: String match to name in use The generated attribute error isn't clear at all, the file actually gets created, but then fails in the processes of writing. There is no clear connection to the netCDF format.

Expected Output

A new file created/written in (default) NETCDF4 format with contents of the Dataset. Or at the very least provide an exception that clearly indicates the format incompatibilities.

#### Output of ``xr.show_versions()`` INSTALLED VERSIONS ------------------ commit: None python: 2.7.5 (default, Sep 12 2018, 05:31:16) [GCC 4.8.5 20150623 (Red Hat 4.8.5-36)] python-bits: 64 OS: Linux OS-release: 3.10.0-957.5.1.el7.x86_64 machine: x86_64 processor: x86_64 byteorder: little LC_ALL: None LANG: en_US.UTF-8 LOCALE: None.None libhdf5: 1.8.18 libnetcdf: 4.4.1.1 xarray: 0.11.3 pandas: 0.22.0 numpy: 1.14.2 scipy: 1.0.0 netCDF4: 1.4.1 pydap: None h5netcdf: None h5py: 2.7.1 Nio: None zarr: None cftime: 1.0.1 PseudonetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None cyordereddict: None dask: None distributed: None matplotlib: 1.2.0 cartopy: None seaborn: None setuptools: 40.4.3 pip: 18.1 conda: None pytest: None IPython: None sphinx: None 
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