issues: 429914958

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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
429914958 MDU6SXNzdWU0Mjk5MTQ5NTg= 2871 xr.open_dataset(f1).to_netcdf(file2) is not idempotent 40218891 closed 0     5 2019-04-05T20:06:35Z 2019-06-12T15:32:27Z 2019-06-12T15:32:27Z NONE      

Here is the original (much truncated) file. ```

ncdump ak.nc netcdf ak { dimensions: npts = UNLIMITED ; // (2 currently) ntimes = 4 ; variables: short tmpk(npts, ntimes) ; tmpk:description = "2 m Temperature - closest to top of hour" ; tmpk:units = "K" ; tmpk:level = "2 m" ; tmpk:period_variable = "ntimes1" ; tmpk:missing_value = -9999s ; tmpk:scale_factor = 0.01 ;

// global attributes: :source = "ak-obs" ; data:

tmpk = 26915, 27755, -9999, 27705, 25595, -9999, 28315, -9999 ; } Python code: ds = xr.open_dataset('ak.nc') ds.to_netcdf('akbad.nc') ds ds['tmpk']

<xarray.Dataset> Dimensions: (npts: 2, ntimes: 4) Dimensions without coordinates: npts, ntimes Data variables: tmpk (npts, ntimes) float32 ... Attributes: source: ak-obs

<xarray.DataArray 'tmpk' (npts: 2, ntimes: 4)> array([[269.15, 277.55, nan, 277.05], [255.95, nan, 283.15, nan]], dtype=float32) Dimensions without coordinates: npts, ntimes Attributes: description: 2 m Temperature - closest to top of hour units: K level: 2 m period_variable: ntimes1 File written to disk:

ncdump akbad.nc netcdf akbad { dimensions: npts = UNLIMITED ; // (2 currently) ntimes = 4 ; variables: short tmpk(npts, ntimes) ; tmpk:description = "2 m Temperature - closest to top of hour" ; tmpk:units = "K" ; tmpk:level = "2 m" ; tmpk:period_variable = "ntimes1" ; tmpk:scale_factor = 0.01 ;

// global attributes: :source = "ak-obs" ; data:

tmpk = 26915, 27755, 0, 27705, 25595, 0, 28315, 0 ; } To confuse matter more, I am getting a warning: SerializationWarning: saving variable tmpk with floating point data as an integer dtype without any _FillValue to use for NaNs `` This might make sense, sincetmpkafter decoding has datatypefloat32, however somehow the original variable type andscale_factorare preserved, butmissing_valueattribute disappears and value written back is wrong: 0. I want to write backtmpk` as float number and let zlib worry about disk space.

xr.show_versions() INSTALLED VERSIONS

commit: None python: 3.7.1 | packaged by conda-forge | (default, Feb 18 2019, 01:42:00) [GCC 7.3.0] 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: en_US.UTF-8 libhdf5: 1.10.4 libnetcdf: 4.6.2

xarray: 0.12.0 pandas: 0.24.2 numpy: 1.15.4 scipy: 1.2.1 netCDF4: 1.5.0 pydap: None h5netcdf: None h5py: None Nio: None zarr: None cftime: 1.0.3.4 nc_time_axis: None PseudonetCDF: None rasterio: None cfgrib: None iris: None bottleneck: None dask: 1.1.4 distributed: 1.26.0 matplotlib: 3.0.3 cartopy: 0.17.0 seaborn: 0.9.0 setuptools: 40.8.0 pip: 19.0.3 conda: 4.6.10 pytest: 4.3.1 IPython: 7.4.0 sphinx: 1.8.5

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