From 5f1b05f5faea4d00f0d5d359b2fc868a4f0a3c10 Mon Sep 17 00:00:00 2001
From: shimwell <mail@jshimwell.com>
Date: Mon, 29 Aug 2022 17:01:34 +0100
Subject: [PATCH 1/3] added element filter to get_nuclide

---
 openmc/material.py                | 22 ++++++++++++++++++----
 tests/unit_tests/test_material.py | 17 +++++++++++++++++
 2 files changed, 35 insertions(+), 4 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index d9d4f241d3..ac8e73afe6 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -795,16 +795,30 @@ class Material(IDManagerMixin):
 
         return sorted({re.split(r'(\d+)', i)[0] for i in self.get_nuclides()})
 
-    def get_nuclides(self):
-        """Returns all nuclides in the material
+    def get_nuclides(self, element: Optional[str] = None):
+        """Returns a list of all nuclides in the material, if the element
+        argument is specified then just nuclides of that element are returned.
+
+        Parameters
+        ----------
+        element : str
+            Specifies the element to match when searching through the nuclides
 
         Returns
         -------
         nuclides : list of str
             List of nuclide names
-
         """
-        return [x.name for x in self._nuclides]
+
+        if element:
+            matching_nuclides = []
+            for nuclide in self._nuclides:
+                if re.split(r'(\d+)', nuclide.name)[0] == element:
+                    matching_nuclides.append(nuclide.name)
+            return list(set(matching_nuclides))
+
+        else:
+            return list(set([x.name for x in self._nuclides]))
 
     def get_nuclide_densities(self):
         """Returns all nuclides in the material and their densities
diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 8bb8817958..8879119a1f 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -299,6 +299,23 @@ def test_isotropic():
     assert m2.isotropic == ['H1']
 
 
+def test_get_nuclides():
+    mat = openmc.Material()
+
+    mat.add_nuclide('Li6', 1.0)
+    assert mat.get_nuclides() == ['Li6']
+    assert mat.get_nuclides(element='Li') == ['Li6']
+    assert mat.get_nuclides(element='Be') == []
+
+    mat.add_element('Li', 1.0)
+    assert mat.get_nuclides() == ['Li7', 'Li6']
+    assert mat.get_nuclides(element='Be') == []
+
+    mat.add_element('Be', 1.0)
+    assert mat.get_nuclides() == ['Li7', 'Li6', 'Be9']
+    assert mat.get_nuclides(element='Be') == ['Be9']
+
+
 def test_get_elements():
     # test that zero elements exist on creation
     m = openmc.Material()

From b857fbd261f4f04136afee6d80b35d740cbe818c Mon Sep 17 00:00:00 2001
From: shimwell <mail@jshimwell.com>
Date: Mon, 29 Aug 2022 18:10:52 +0100
Subject: [PATCH 2/3] appending to list if not in list

---
 openmc/material.py | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/openmc/material.py b/openmc/material.py
index ac8e73afe6..f137ec0cd7 100644
--- a/openmc/material.py
+++ b/openmc/material.py
@@ -810,15 +810,18 @@ class Material(IDManagerMixin):
             List of nuclide names
         """
 
+        matching_nuclides = []
         if element:
-            matching_nuclides = []
             for nuclide in self._nuclides:
                 if re.split(r'(\d+)', nuclide.name)[0] == element:
-                    matching_nuclides.append(nuclide.name)
-            return list(set(matching_nuclides))
-
+                    if nuclide.name not in matching_nuclides:
+                        matching_nuclides.append(nuclide.name)
         else:
-            return list(set([x.name for x in self._nuclides]))
+            for nuclide in self._nuclides:
+                if nuclide.name not in matching_nuclides:
+                    matching_nuclides.append(nuclide.name)
+                        
+        return matching_nuclides
 
     def get_nuclide_densities(self):
         """Returns all nuclides in the material and their densities

From 5a0884e9de34cfcaf5cd16dccfb3f28303d962d5 Mon Sep 17 00:00:00 2001
From: shimwell <mail@jshimwell.com>
Date: Mon, 29 Aug 2022 22:41:07 +0100
Subject: [PATCH 3/3] corrected get nuclide tests

---
 tests/unit_tests/test_material.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/unit_tests/test_material.py b/tests/unit_tests/test_material.py
index 8879119a1f..26ccbc9feb 100644
--- a/tests/unit_tests/test_material.py
+++ b/tests/unit_tests/test_material.py
@@ -308,11 +308,11 @@ def test_get_nuclides():
     assert mat.get_nuclides(element='Be') == []
 
     mat.add_element('Li', 1.0)
-    assert mat.get_nuclides() == ['Li7', 'Li6']
+    assert mat.get_nuclides() == ['Li6', 'Li7']
     assert mat.get_nuclides(element='Be') == []
 
     mat.add_element('Be', 1.0)
-    assert mat.get_nuclides() == ['Li7', 'Li6', 'Be9']
+    assert mat.get_nuclides() == ['Li6', 'Li7', 'Be9']
     assert mat.get_nuclides(element='Be') == ['Be9']