From 5574acc117fc80c913fa8b7f4cf8a08052ac3b65 Mon Sep 17 00:00:00 2001
From: Florian Ludwig <f.ludwig@greyrook.com>
Date: Fri, 23 Oct 2020 23:17:50 +0200
Subject: optimize sparql.Bindings

---
 rdflib/plugins/sparql/sparql.py | 21 +++++++++++----------
 test/test_sparql.py             | 19 +++++++++++++++++++
 2 files changed, 30 insertions(+), 10 deletions(-)

diff --git a/rdflib/plugins/sparql/sparql.py b/rdflib/plugins/sparql/sparql.py
index f24aa564..a98bfb4c 100644
--- a/rdflib/plugins/sparql/sparql.py
+++ b/rdflib/plugins/sparql/sparql.py
@@ -52,12 +52,12 @@ class Bindings(MutableMapping):
         self.outer = outer
 
     def __getitem__(self, key):
-        try:
+        if key in self._d:
             return self._d[key]
-        except KeyError:
-            if not self.outer:
-                raise
-            return self.outer[key]
+        
+        if not self.outer:
+            raise KeyError()
+        return self.outer[key]
 
     def __contains__(self, key):
         try:
@@ -72,17 +72,18 @@ class Bindings(MutableMapping):
     def __delitem__(self, key):
         raise Exception("DelItem is not implemented!")
 
-    def __len__(self):
+    def __len__(self) -> int:
         i = 0
-        for x in self:
-            i += 1
+        d = self
+        while d is not None:
+            i += len(d._d)
+            d = d.outer
         return i
 
     def __iter__(self):
         d = self
         while d is not None:
-            for i in dict.__iter__(d._d):
-                yield i
+            yield from d._d
             d = d.outer
 
     def __str__(self):
diff --git a/test/test_sparql.py b/test/test_sparql.py
index fdf29c3c..cabb9411 100644
--- a/test/test_sparql.py
+++ b/test/test_sparql.py
@@ -1,3 +1,4 @@
+from rdflib.plugins.sparql import sparql
 from rdflib import Graph, URIRef, Literal, BNode
 from rdflib.plugins.sparql import prepareQuery
 from rdflib.compare import isomorphic
@@ -112,6 +113,24 @@ def test_sparql_update_with_bnode_serialize_parse():
     assert not raised
 
 
+def test_bindings():
+    layer_0 = sparql.Bindings(d={"v": 1, "bar": 2})
+    layer_1 = sparql.Bindings(outer=layer_0, d={"v": 3})
+
+
+    assert layer_0["v"] == 1
+    assert layer_1["v"] == 3
+    assert layer_1["bar"] == 2
+
+    assert "foo" not in layer_0
+    assert "v" in layer_0
+    assert "bar" in layer_1
+
+    # XXX This might not be intendet behaviour
+    #     but is kept for compatibility for now.
+    assert len(layer_1) == 3
+
+
 if __name__ == "__main__":
     import nose
 
-- 
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