Add a method to return a CubeList from CubeList.copy() (#4094)

* Add a method to return a CubeList from CubeList.copy()

* Created an entry in What's New

* Added test for CubeList.copy()

* Moved CubeList.copy() test into the correct file

* Creating a link to the username

docs/src/whatsnew/latest.rst

@@ -52,6 +52,9 @@ This document explains the changes made to Iris for this release
    printing these objects skips metadata elements that are set to None or an
    empty string or dictionary. (:pull:`4040`)
 
+#. `@Badboy-16`_ implemented a ``CubeList.copy()`` method to return a
+   ``CubeList`` object instead of a ``list``. (:pull:`4094`)
+
 
 🐛 Bugs Fixed
 =============
@@ -170,6 +173,7 @@ This document explains the changes made to Iris for this release
     core dev names are automatically included by the common_links.inc:
 
 .. _@akuhnregnier: https://github.com/akuhnregnier
+.. _@Badboy-16: https://github.com/Badboy-16
 .. _@gcaria: https://github.com/gcaria
 .. _@MHBalsmeier: https://github.com/MHBalsmeier
 
@@ -189,4 +193,4 @@ This document explains the changes made to Iris for this release
 .. _Python 3.8: https://www.python.org/downloads/release/python-380/
 .. _README.md: https://github.com/SciTools/iris#-----
 .. _xxhash: http://cyan4973.github.io/xxHash/
-.. _conda-lock: https://github.com/conda-incubator/conda-lock
+.. _conda-lock: https://github.com/conda-incubator/conda-lock

lib/iris/cube.py

@@ -707,6 +707,13 @@ def realise_data(self):
         """
         _lazy.co_realise_cubes(*self)
 
+    def copy(self):
+        """
+        Return a CubeList when CubeList.copy() is called.
+        """
+        if type(self) == CubeList:
+            return deepcopy(self)
+
 
 def _is_single_item(testee):
     """

lib/iris/tests/unit/cube/test_CubeList.py

@@ -602,5 +602,14 @@ def test_realise_data(self):
         )
 
 
+class Test_CubeList_copy(tests.IrisTest):
+    def setUp(self):
+        self.cube_list = iris.cube.CubeList()
+        self.copied_cube_list = self.cube_list.copy()
+
+    def test_copy(self):
+        self.assertIsInstance(self.copied_cube_list, iris.cube.CubeList)
+
+
 if __name__ == "__main__":
     tests.main()