Class NetCDF4BackendEntrypoint

xarray/backends/netCDF4_.py:680–906

Backend for netCDF files based on the netCDF4 package. It can open ".nc", ".nc4", ".cdf" files and will be chosen as default for these files. Additionally it can open valid HDF5 files, see https://h5netcdf.org/#invalid-netcdf-files for more info. It will not be detected as

class NetCDF4BackendEntrypoint(BackendEntrypoint):
    """
    Backend for netCDF files based on the netCDF4 package.

    It can open ".nc", ".nc4", ".cdf" files and will be chosen
    as default for these files.

    Additionally it can open valid HDF5 files, see
    https://h5netcdf.org/#invalid-netcdf-files for more info.
    It will not be detected as valid backend for such files, so make
    sure to specify ``engine="netcdf4"`` in ``open_dataset``.

    For more information about the underlying library, visit:
    https://unidata.github.io/netcdf4-python

    See Also
    --------
    backends.NetCDF4DataStore
    backends.H5netcdfBackendEntrypoint
    backends.ScipyBackendEntrypoint
    """

    description = (
        "Open netCDF (.nc, .nc4 and .cdf) and most HDF5 files using netCDF4 in Xarray"
    )
    url = "https://docs.xarray.dev/en/stable/generated/xarray.backends.NetCDF4BackendEntrypoint.html"
    supports_groups = True

    def guess_can_open(self, filename_or_obj: T_PathFileOrDataStore) -> bool:
        # Helper to check if magic number is netCDF or HDF5
        def _is_netcdf_magic(magic: bytes) -> bool:
            return magic.startswith((b"CDF", b"\211HDF\r\n\032\n"))

        # Helper to check if extension is netCDF
        def _has_netcdf_ext(path: str | os.PathLike, is_remote: bool = False) -> bool:
            path = str(path).rstrip("/")
            # For remote URIs, strip query parameters and fragments
            if is_remote:
                path = strip_uri_params(path)
            _, ext = os.path.splitext(path)
            return ext in {".nc", ".nc4", ".cdf"}

        if isinstance(filename_or_obj, str):
            if is_remote_uri(filename_or_obj):
                # For remote URIs, check extension (accounting for query params/fragments)
                # Remote netcdf-c can handle both regular URLs and DAP URLs
                if _has_netcdf_ext(filename_or_obj, is_remote=True):
                    return True
                elif "zarr" in filename_or_obj.lower():
                    return False
                # return true for non-zarr URLs so we don't have a breaking change for people relying on this
                # netcdf backend guessing true for all remote sources.
                # TODO: emit a warning here about deprecation of this behavior
                # https://github.com/pydata/xarray/pull/10931
                return True

        if isinstance(filename_or_obj, str | os.PathLike):
            # For local paths, check magic number first, then extension