diff --git a/Lib/_strptime.py b/Lib/_strptime.py --- a/Lib/_strptime.py +++ b/Lib/_strptime.py @@ -326,7 +326,7 @@ bad_directive = "%" del err raise ValueError("'%s' is a bad directive in format '%s'" % - (bad_directive, format)) + (bad_directive, format)) from None # IndexError only occurs when the format string is "%" except IndexError: raise ValueError("stray %% in format '%s'" % format) diff --git a/Lib/test/test_strptime.py b/Lib/test/test_strptime.py --- a/Lib/test/test_strptime.py +++ b/Lib/test/test_strptime.py @@ -218,6 +218,12 @@ else: self.fail("'%s' did not raise ValueError" % bad_format) + def test_strptime_exception_context(self): + # check that this doesn't chain exceptions needlessly (see #17572) + with self.assertRaises(ValueError) as e: + _strptime._strptime_time('', '%D') + self.assertIs(e.exception.__suppress_context__, True) + def test_unconverteddata(self): # Check ValueError is raised when there is unconverted data self.assertRaises(ValueError, _strptime._strptime_time, "10 12", "%m") diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py --- a/Lib/test/test_time.py +++ b/Lib/test/test_time.py @@ -193,6 +193,12 @@ self.assertRaises(TypeError, time.strptime, b'2009', "%Y") self.assertRaises(TypeError, time.strptime, '2009', b'%Y') + def test_strptime_exception_context(self): + # check that this doesn't chain exceptions needlessly (see #17572) + with self.assertRaises(ValueError) as e: + time.strptime('', '%D') + self.assertIs(e.exception.__suppress_context__, True) + def test_asctime(self): time.asctime(time.gmtime(self.t))