1 files changed, 20 insertions, 14 deletions
diff --git a/rdflib/plugins/sparql/processor.py b/rdflib/plugins/sparql/processor.py
index c2fb7e54..f10f372b 100644
--- a/rdflib/plugins/sparql/processor.py
+++ b/rdflib/plugins/sparql/processor.py
@@ -19,22 +19,30 @@ from rdflib.term import Identifier
 
 
 def prepareQuery(
-    queryString: str, initNs: Mapping[str, Any] = {}, base: Optional[str] = None
+    queryString: str,
+    initNs: Optional[Mapping[str, Any]] = None,
+    base: Optional[str] = None,
 ) -> Query:
     """
     Parse and translate a SPARQL Query
     """
+    if initNs is None:
+        initNs = {}
     ret = translateQuery(parseQuery(queryString), base, initNs)
     ret._original_args = (queryString, initNs, base)
     return ret
 
 
 def prepareUpdate(
-    updateString: str, initNs: Mapping[str, Any] = {}, base: Optional[str] = None
+    updateString: str,
+    initNs: Optional[Mapping[str, Any]] = None,
+    base: Optional[str] = None,
 ) -> Update:
     """
     Parse and translate a SPARQL Update
     """
+    if initNs is None:
+        initNs = {}
     ret = translateUpdate(parseUpdate(updateString), base, initNs)
     ret._original_args = (updateString, initNs, base)
     return ret
@@ -43,8 +51,8 @@ def prepareUpdate(
 def processUpdate(
     graph: Graph,
     updateString: str,
-    initBindings: Mapping[str, Identifier] = {},
-    initNs: Mapping[str, Any] = {},
+    initBindings: Optional[Mapping[str, Identifier]] = None,
+    initNs: Optional[Mapping[str, Any]] = None,
     base: Optional[str] = None,
 ) -> None:
     """
@@ -73,8 +81,8 @@ class SPARQLUpdateProcessor(UpdateProcessor):
     def update(
         self,
         strOrQuery: Union[str, Update],
-        initBindings: Mapping[str, Identifier] = {},
-        initNs: Mapping[str, Any] = {},
+        initBindings: Optional[Mapping[str, Identifier]] = None,
+        initNs: Optional[Mapping[str, Any]] = None,
     ) -> None:
         """
         .. caution::
@@ -108,8 +116,8 @@ class SPARQLProcessor(Processor):
     def query(  # type: ignore[override]
         self,
         strOrQuery: Union[str, Query],
-        initBindings: Mapping[str, Identifier] = {},
-        initNs: Mapping[str, Any] = {},
+        initBindings: Optional[Mapping[str, Identifier]] = None,
+        initNs: Optional[Mapping[str, Any]] = None,
         base: Optional[str] = None,
         DEBUG: bool = False,
     ) -> Mapping[str, Any]:
@@ -132,9 +140,7 @@ class SPARQLProcessor(Processor):
            documentation.
         """
 
-        if not isinstance(strOrQuery, Query):
-            parsetree = parseQuery(strOrQuery)
-            query = translateQuery(parsetree, base, initNs)
-        else:
-            query = strOrQuery
-        return evalQuery(self.graph, query, initBindings, base)
+        if isinstance(strOrQuery, str):
+            strOrQuery = translateQuery(parseQuery(strOrQuery), base, initNs)
+
+        return evalQuery(self.graph, strOrQuery, initBindings, base)