Make scipy import no longer lazy

Author: shoyer

xarray/backends/scipy_.py

@@ -35,6 +35,12 @@
 )
 from xarray.core.variable import Variable
 
+try:
+    from scipy.io import netcdf_file as netcdf_file_base
+except ImportError:
+    netcdf_file_base = object
+
+
 if TYPE_CHECKING:
     import scipy.io
 
@@ -104,31 +110,32 @@ def __setitem__(self, key, value):
                     raise
 
 
+# TODO: Make the scipy import lazy again after upstreaming these fixes.
+class flush_only_netcdf_file(netcdf_file_base):
+    # scipy.io.netcdf_file.close() incorrectly closes file objects that
+    # were passed in as constructor arguments:
+    # https://github.com/scipy/scipy/issues/13905
+
+    # Instead of closing such files, only call flush(), which is
+    # equivalent as long as the netcdf_file object is not mmapped.
+    # This suffices to keep BytesIO objects open long enough to read
+    # their contents from to_netcdf(), but underlying files still get
+    # closed when the netcdf_file is garbage collected (via __del__),
+    # and will need to be fixed upstream in scipy.
+    def close(self):
+        if hasattr(self, "fp") and not self.fp.closed:
+            self.flush()
+            self.fp.seek(0)  # allow file to be read again
+
+    def __del__(self):
+        # Remove the __del__ method, which in scipy is aliased to close().
+        # These files need to be closed explicitly by xarray.
+        pass
+
+
 def _open_scipy_netcdf(filename, mode, mmap, version, flush_only=False):
     import scipy.io
 
-    # define inside a helper function to ensure the scipy import is lazy
-    class flush_only_netcdf_file(scipy.io.netcdf_file):
-        # scipy.io.netcdf_file.close() incorrectly closes file objects that
-        # were passed in as constructor arguments:
-        # https://github.com/scipy/scipy/issues/13905
-
-        # Instead of closing such files, only call flush(), which is
-        # equivalent as long as the netcdf_file object is not mmapped.
-        # This suffices to keep BytesIO objects open long enough to read
-        # their contents from to_netcdf(), but underlying files still get
-        # closed when the netcdf_file is garbage collected (via __del__),
-        # and will need to be fixed upstream in scipy.
-        def close(self):
-            if hasattr(self, "fp") and not self.fp.closed:
-                self.flush()
-                self.fp.seek(0)  # allow file to be read again
-
-        def __del__(self):
-            # Remove the __del__ method, which in scipy is aliased to close().
-            # These files need to be closed explicitly by xarray.
-            pass
-
     netcdf_file = flush_only_netcdf_file if flush_only else scipy.io.netcdf_file
 
     # if the string ends with .gz, then gunzip and open as netcdf file

xarray/tests/test_plugins.py

@@ -227,7 +227,7 @@ def test_lazy_import() -> None:
         "numbagg",
         "pint",
         "pydap",
-        "scipy",
+        # "scipy",  # TODO: xarray.backends.scipy_ is currently not lazy
         "sparse",
         "zarr",
     ]