added asserts for graph.set([s,p,o]) so s and p aren't None

otherwise this will delete (*, p, *) or (s, *, *) or even (*, *, *) from graph
and fails on add which is most likely not what the developer wants.

1 files changed, 6 insertions, 2 deletions

diff --git a/rdflib/graph.py b/rdflib/graph.py
index dbbe67c8..68339eba 100644
--- a/rdflib/graph.py
+++ b/rdflib/graph.py
@@ -611,9 +611,13 @@ class Graph(Node):
         Remove any existing triples for subject and predicate before adding
         (subject, predicate, object).
         """
-        (subject, predicate, object) = triple
+        (subject, predicate, object_) = triple
+        assert subject is not None, \
+            "s can't be None in .set([s,p,o]), as it would remove (*, p, *)"
+        assert predicate is not None, \
+            "p can't be None in .set([s,p,o]), as it would remove (s, *, *)"
         self.remove((subject, predicate, None))
-        self.add((subject, predicate, object))
+        self.add((subject, predicate, object_))
 
     def subjects(self, predicate=None, object=None):
         """A generator of subjects with the given predicate and object"""