extract len() out of loop

Author: alessandro-nori

pyiceberg/catalog/sql.py

@@ -626,8 +626,9 @@ def list_namespaces(self, namespace: Union[str, Identifier] = ()) -> List[Identi
 
             if namespace:
                 namespace_tuple = Catalog.identifier_to_tuple(namespace)
+                namespace_level_length = len(namespace_tuple)
                 # exclude fuzzy matches when `namespace` contains `%` or `_`
-                namespaces = [ns for ns in namespaces if ns[: len(namespace_tuple)] == namespace_tuple]
+                namespaces = [ns for ns in namespaces if ns[:namespace_level_length] == namespace_tuple]
 
             return namespaces