use . as default stream name

diff --git a/sdk/python/arvados.py b/sdk/python/arvados.py
index 5a15250a8d323d04c144b3b4d1077016e70e9b0f..569af34e8b5f95b70493c125f9c8d3d4490f3a58 100644 (file)
--- a/sdk/python/arvados.py
+++ b/sdk/python/arvados.py
@@ -615,7 +615,7 @@ class CollectionWriter:
                                        self._current_stream_length - self._current_file_pos,
                                        self._current_file_name]]
         self._current_file_pos = self._current_stream_length
-    def start_new_stream(self, newstreamname=None):
+    def start_new_stream(self, newstreamname='.'):
         self.finish_current_stream()
         self.set_current_stream_name(newstreamname)
     def set_current_stream_name(self, newstreamname):