Also make the str() value match betwenn C and Python TimeStamp objects; test this.

persistent/tests/test_timestamp.py

@@ -192,6 +192,11 @@ class PyAndCComparisonTests(unittest.TestCase):
             c, py = self._make_C_and_Py(*args)
             self.assertEqual(repr(c), repr(py))
 
+    def test_strs_equal(self):
+        for args in self._make_many_instants():
+            c, py = self._make_C_and_Py(*args)
+            self.assertEqual(str(c), str(py))
+
     def test_raw_equal(self):
         c, py = self._make_C_and_Py(*self.now_ts_args)
         self.assertEqual(c.raw(), py.raw())

persistent/timestamp.py

@@ -91,6 +91,12 @@ class pyTimeStamp(object):
     def __repr__(self):
         return repr(self._raw)
 
+    def __str__(self):
+        return "%4.4d-%2.2d-%2.2d %2.2d:%2.2d:%09.6f" % (
+            self.year(), self.month(), self.day(),
+            self.hour(), self.minute(),
+            self.second())
+
     def year(self):
         return self._elements[0]