"DLL load failed while importing _netCDF4" with netCDF-C 4.9.0 and HDF5 1.10.8

[abhibaruah]

Version : netCDF4-python 1.6.2 OS: Windows 10 Python version: 3.11.1

I am trying to follow the steps from the page (https://unidata.github.io/netcdf4-python/#developer-install) to build netCDF4-Python v1.6.3 with netCDF-C and HDF5 that we build ourselves (instead of using the pip package manager).

Our netCDF-C version is 4.9.0, and we have linked it to HDF5 1.10.8. With these versions of netCDF-C and HDF5, the netCDF4-Python build goes fine but when I execute "import netCDF4", I see the following error:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\abaruah\AppData\Local\Programs\Python\Python311\Lib\site-packages\netcdf4-1.6.2-py3.11-win-amd64.egg\netCDF4\__init__.py", line 3, in <module>
    from ._netCDF4 import *
ImportError: DLL load failed while importing _netCDF4: The specified module could not be found.

I do not see the error and everything works fine if I download the netCDF-C v4.9.0 binaries from the following site (https://downloads.unidata.ucar.edu/netcdf/). Here, netCDF-C is built with HDF5 1.12.1.

Is there a requirement for the HDF5 version to be 1.12.1 or is HDF5 v1.10.8 not supported in netCDF-C v1.6.2? If not, can some help me to resolve this error?

[jswhit]

Although you say the build went fine, something likely went wrong with either the build or install. I would suggest saving the output of the build and posting it here. HDF5 1.10.8 should work fine.

[abhibaruah]

Please find the output of 'python setup.py build' and 'python setup.py install' in the two files build.log and install.log respectively. build.log install.log

Another thing I would like to mention is that for 'import netCDF4' to actually work, I have to copy the extracted binaries from the 'bin' folder (from the Unidata netCDF page) to the folder 'AppData\Local\Programs\Python\Python311\Lib\site-packages\netCDF4-1.6.2-py3.11-win-amd64.egg\netCDF4'. I get the errors I mentioned in the problem description if I copy the binaries from the bin folder of the netCDF-C v4.9.0 that I built (and not downloaded).

Even if I set the HDF5_DIR and NETCDF4_DIR env variables to the location of my netCDF binaries while building netCDF4-Python, 'import netCDF4' works only if I copy the Unidata binaries.

[jswhit]

hopefully someone with some knowledge of building and installing python C extensions with C lib dependencies on windows will chime in - I have no clue. Curious why installing via pip or conda is not an option for you?

[abhibaruah]

conda is not an option for us because of legal restrictions in our organization. We want to build from source (developer install) because we want to use netCDF4-Python with netCDF-C v4.9.0 and HDF5 v1.10.8. pip does not install these versions of netCDF-C and HDF5.

[jamesmhbarry]

I am having the same issue when using conda:

File ~\AppData\Local\anaconda3\lib\site-packages\xarray\backends\api.py:566 in open_dataset
    backend_ds = backend.open_dataset(

  File ~\AppData\Local\anaconda3\lib\site-packages\xarray\backends\netCDF4_.py:590 in open_dataset
    store = NetCDF4DataStore.open(

  File ~\AppData\Local\anaconda3\lib\site-packages\xarray\backends\netCDF4_.py:358 in open
    import netCDF4

  File ~\AppData\Local\anaconda3\lib\site-packages\netCDF4\__init__.py:3
    from ._netCDF4 import *

ImportError: DLL load failed while importing _netCDF4: The specified procedure could not be found.```

[ocefpaf]

I am having the same issue when using conda

Please open an issue in the proper conda channel. If that is conda-forge it should be in https://github.com/conda-forge/netcdf4-feedstock

[jamesmhbarry]

I am having the same issue when using conda

Please open an issue in the proper conda channel. If that is conda-forge it should be in https://github.com/conda-forge/netcdf4-feedstock

I am not sure it really is conda-forge since the version I have installed is 1.6.2, installed using conda install netcdf4

[ocefpaf]

I am not sure it really is conda-forge since the version I have installed is 1.6.2, installed using conda install netcdf4

The template issue there will request some information that will help you sort that out. Just follow the instructions there.