- New function sys.exc_clear() clears the current exception. This is

  rarely needed, but can sometimes be useful to release objects
  referenced by the traceback held in sys.exc_info()[2].  (SF patch
  #693195.)  Thanks to Kevin Jacobs!

1 files changed, 44 insertions, 0 deletions

diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index b18b0c7..2afac65 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -63,6 +63,50 @@ class SysModuleTest(unittest.TestCase):
     # FIXME: testing the code for a lost or replaced excepthook in
     # Python/pythonrun.c::PyErr_PrintEx() is tricky.
 
+    def test_exc_clear(self):
+        self.assertRaises(TypeError, sys.exc_clear, 42)
+
+        # Verify that exc_info is present and matches exc, then clear it, and
+        # check that it worked.
+        def clear_check(exc):
+          typ, value, traceback = sys.exc_info()
+          self.assert_(typ is not None)
+          self.assert_(value is exc)
+          self.assert_(traceback is not None)
+
+          sys.exc_clear()
+
+          typ, value, traceback = sys.exc_info()
+          self.assert_(typ is None)
+          self.assert_(value is None)
+          self.assert_(traceback is None)
+
+        def clear():
+          try:
+            raise ValueError, 42
+          except ValueError, exc:
+            clear_check(exc)
+
+        # Raise an exception and check that it can be cleared
+        clear()
+
+        # Verify that a frame currently handling an exception is
+        # unaffected by calling exc_clear in a nested frame.
+        try:
+          raise ValueError, 13
+        except ValueError, exc:
+          typ1, value1, traceback1 = sys.exc_info()
+          clear()
+          typ2, value2, traceback2 = sys.exc_info()
+
+          self.assert_(typ1 is typ2)
+          self.assert_(value1 is exc)
+          self.assert_(value1 is value2)
+          self.assert_(traceback1 is traceback2)
+
+        # Check that an exception can be cleared outside of an except block
+        clear_check(exc)
+
     def test_exit(self):
         self.assertRaises(TypeError, sys.exit, 42, 42)