support Pathlike in Dataset.fromcdl

.gitignore

@@ -13,3 +13,4 @@ netcdftime/_netcdftime.c
 venv/
 .eggs/
 .idea/
+.vscode/

Changelog

@@ -1,5 +1,7 @@
  since version 1.7.2 release
  ===========================
+ * support os.PathLike arguments for `Dataset.fromcdl` and raise a `FileNotFoundError`
+   if the cdl is missing and a `FileExistsError` if the nc file already exists (PR #1387)
  * raise more informative error when trying to iterate or
    perform a membership operation on a Dataset (issue #1383)
  * fix type hint for createEnumType (issue #1378)

src/netCDF4/__init__.pyi

@@ -373,7 +373,7 @@ class Dataset:
     def get_variables_by_attributes(self, **kwargs: Callable[[Any], bool] | Any) -> list[Variable]: ...
     @staticmethod
     def fromcdl(
-        cdlfilename: str, ncfilename: str | None = None, mode: AccessMode = "a", format: Format = "NETCDF4"
+        cdlfilename: str | os.PathLike, ncfilename: str | os.PathLike | None = None, mode: AccessMode = "a", format: Format = "NETCDF4"
     ) -> Dataset: ...
     @overload
     def tocdl(self, coordvars: bool = False, data: bool = False, outfile: None = None) -> str: ...

src/netCDF4/_netCDF4.pyx

@@ -3502,19 +3502,27 @@ Dataset instance for `ncfilename` is returned.
 [ncgen]: https://www.unidata.ucar.edu/software/netcdf/docs/netcdf_utilities_guide.html#ncgen_guide
 [cdl]: https://www.unidata.ucar.edu/software/netcdf/docs/netcdf_utilities_guide.html#cdl_guide
         """
+        filepath = pathlib.Path(cdlfilename)
         if ncfilename is None:
-            filepath = pathlib.Path(cdlfilename)
             ncfilename = filepath.with_suffix('.nc')
+        else:
+            ncfilename = pathlib.Path(ncfilename)
         formatcodes = {'NETCDF4': 4,
                        'NETCDF4_CLASSIC': 7,
                        'NETCDF3_CLASSIC': 3,
                        'NETCDF3_64BIT': 6, # legacy
                        'NETCDF3_64BIT_OFFSET': 6,
                        'NETCDF3_64BIT_DATA': 5}
+
         if format not in formatcodes:
             raise ValueError('illegal format requested')
+        if not filepath.exists():
+            raise FileNotFoundError(filepath)
+        if ncfilename.exists():
+            raise FileExistsError(ncfilename)
+
         ncgenargs="-knc%s" % formatcodes[format]
-        subprocess.run(["ncgen", ncgenargs, "-o", ncfilename, cdlfilename], check=True)
+        subprocess.run(["ncgen", ncgenargs, "-o", str(ncfilename), str(filepath)], check=True)
         return Dataset(ncfilename, mode=mode)
 
     def tocdl(self,coordvars=False,data=False,outfile=None):

test/test_cdl.py

@@ -68,8 +68,18 @@ def test_fromcdl(self):
                 assert len(f1.dimensions["d"]) == len(f2.dimensions["d"])
                 assert (f1["ub"][:] == f2["ub"][:]).all()
                 assert (f1["sb"][:] == f2["sb"][:]).all()
+
+            # test if os.PathLike works
+            with netCDF4.Dataset.fromcdl(pathlib.Path("ubyte.cdl"), ncfilename=pathlib.Path("ubyte3.nc")) as f3:
+                assert f1.variables.keys() == f3.variables.keys()
 
+        # check if correct errors are raised
+        self.assertRaises(FileNotFoundError, netCDF4.Dataset.fromcdl, "doesnotexist.cdl")
+        self.assertRaises(FileExistsError, netCDF4.Dataset.fromcdl, "ubyte.cdl", ncfilename="ubyte2.nc")
+
+        # cleanup
         os.remove("ubyte2.nc")
+        os.remove("ubyte3.nc")
 
     def tearDown(self):
         # Remove the temporary files