Fix memory leak: implement __deepcopy__ for ExtraCoords and GlobalCoords

changelog/991.bugfix.rst

@@ -0,0 +1 @@
+Fixed a memory leak when deep-copying an ``NDCube`` object or its coordinates by properly implementing ``__deepcopy__`` for ``ExtraCoords`` and ``GlobalCoords``.

ndcube/extra_coords/extra_coords.py

@@ -1,4 +1,5 @@
 import abc
+import copy
 from collections.abc import Iterable
 from functools import partial, reduce
 from numbers import Integral
@@ -155,6 +156,18 @@ def __init__(self, ndcube=None):
         # We need a reference to the parent NDCube
         self._ndcube = ndcube
 
+    def __deepcopy__(self, memo):
+
+        cls = self.__class__
+        result = cls.__new__(cls)
+        memo[id(self)] = result
+        for k, v in self.__dict__.items():
+            if k == '_ndcube':
+                setattr(result, k, None)
+            else:
+                setattr(result, k, copy.deepcopy(v, memo))
+        return result
+
     @classmethod
     def from_lookup_tables(cls, names, pixel_dimensions, lookup_tables, physical_types=None):
         """

ndcube/global_coords.py

@@ -88,6 +88,18 @@ def __init__(self, ndcube=None):
         self._ndcube = ndcube
         self._internal_coords = OrderedDict()
 
+    def __deepcopy__(self, memo):
+
+        cls = self.__class__
+        result = cls.__new__(cls)
+        memo[id(self)] = result
+        for k, v in self.__dict__.items():
+            if k == '_ndcube':
+                setattr(result, k, None)
+            else:
+                setattr(result, k, copy.deepcopy(v, memo))
+        return result
+
     @staticmethod
     def _convert_dropped_to_internal(dropped_dimensions):
         """