further improve parallel_for

satella/__init__.py

-__version__ = '2.8.15_a5'
+__version__ = '2.8.15_a6'

satella/cassandra/__init__.py

@@ -14,7 +14,7 @@ def parallel_for(cursor, query: tp.Union[tp.List[str], str, 'Statement', tp.List
     >>> for future in futures:
     >>>     yield future.result()
 
-    If query is a string, or else
+    If query is a string or a Cassandra Statement, or else
 
     >>> futures = []
     >>> for query, args in zip(query, arguments):
@@ -22,6 +22,9 @@ def parallel_for(cursor, query: tp.Union[tp.List[str], str, 'Statement', tp.List
     >>> for future in futures:
     >>>     yield future.result()
 
+    Note that if None is encountered in the argument iterable, session.execute() will
+    be called with a single argument. You better have it as a BoundStatement then!
+
     :param cursor: the Cassandra cursor to use (obtained using connection.session())
     :param query: base query or a list of queries, if a different one is to be used
     :param arguments: iterable yielding arguments to use in execute_async
@@ -30,8 +33,14 @@ def parallel_for(cursor, query: tp.Union[tp.List[str], str, 'Statement', tp.List
 
     if isinstance(query, (str, Statement)):
         query = itertools.repeat(query)
-
-    futures = [cursor.execute_async(query, args) for query, args in zip(query, arguments)]
+    futures = []
+
+    for query, args in zip(query, arguments):
+        if args is None:
+            future = cursor.execute_async(query)
+        else:
+            future = cursor.execute_async(query, args)
+        futures.append(future)
 
     for future in futures:
         yield future.result()

tests/test_cassandra.py

@@ -8,12 +8,15 @@ class TestCassandra(unittest.TestCase):
             def __init__(self):
                 self.execute_times_called = 0
                 self.result_times_called = 0
+                self.execute_without_args_called = 0
 
             def result(self):
                 self.result_times_called += 1
                 return []
 
-            def execute_async(self, query, args):
+            def execute_async(self, query, args=None):
+                if args is None:
+                    self.execute_without_args_called += 1
                 self.execute_times_called += 1
                 return self
 
@@ -29,3 +32,10 @@ class TestCassandra(unittest.TestCase):
 
         self.assertEqual(cur.execute_times_called, 6)
         self.assertEqual(cur.result_times_called, 6)
+
+        list(parallel_for(cur, ['SELECT * FROM table',
+                                'SELECT * FROM table2',
+                                'SELECT * FROM table3'], [None, None, None]))
+
+        self.assertEqual(cur.execute_without_args_called, 3)
+