encapsulates the call stack at the point where the exception
originally occurred. \obindex{traceback}
+ If \function{exc_clear()} is called, this function will return three
+ \code{None} values until either another exception is raised in the
+ current thread or the execution stack returns to a frame where
+ another exception is being handled.
+
\warning{Assigning the \var{traceback} return value to a
local variable in a function that is handling an exception will
cause a circular reference. This will prevent anything referenced
efficient to avoid creating cycles.}
\end{funcdesc}
+\begin{funcdesc}{exc_clear}{}
+ This function clears all information relating to the current or last
+ exception that occured in the current thread. After calling this
+ function, \function{exc_info()} will return three \code{None} values until
+ another exception is raised in the current thread or the execution stack
+ returns to a frame where another exception is being handled.
+
+ This function is only needed in only a few obscure situations. These
+ include logging and error handling systems that report information on the
+ last or current exception. This function can also be used to try to free
+ resources and trigger object finalization, though no guarantee is made as
+ to what objects will be freed, if any.
+\versionadded{2.3}
+\end{funcdesc}
+
\begin{datadesc}{exc_type}
\dataline{exc_value}
\dataline{exc_traceback}
['__name__', 'fib', 'fib2']
>>> dir(sys)
['__displayhook__', '__doc__', '__excepthook__', '__name__', '__stderr__',
- '__stdin__', '__stdout__', '_getframe', 'argv', 'builtin_module_names',
- 'byteorder', 'copyright', 'displayhook', 'exc_info', 'exc_type',
- 'excepthook', 'exec_prefix', 'executable', 'exit', 'getdefaultencoding',
- 'getdlopenflags', 'getrecursionlimit', 'getrefcount', 'hexversion',
- 'maxint', 'maxunicode', 'modules', 'path', 'platform', 'prefix', 'ps1',
- 'ps2', 'setcheckinterval', 'setdlopenflags', 'setprofile',
- 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout', 'version',
- 'version_info', 'warnoptions']
+ '__stdin__', '__stdout__', '_getframe', 'api_version', 'argv',
+ 'builtin_module_names', 'byteorder', 'callstats', 'copyright',
+ 'displayhook', 'exc_clear', 'exc_info', 'exc_type', 'excepthook',
+ 'exec_prefix', 'executable', 'exit', 'getdefaultencoding', 'getdlopenflags',
+ 'getrecursionlimit', 'getrefcount', 'hexversion', 'maxint', 'maxunicode',
+ 'meta_path', 'modules', 'path', 'path_hooks', 'path_importer_cache',
+ 'platform', 'prefix', 'ps1', 'ps2', 'setcheckinterval', 'setdlopenflags',
+ 'setprofile', 'setrecursionlimit', 'settrace', 'stderr', 'stdin', 'stdout',
+ 'version', 'version_info', 'warnoptions']
\end{verbatim}
Without arguments, \function{dir()} lists the names you have defined
# 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)
Core and builtins
-----------------
+
+- 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.)
+
- On 64-bit systems, a dictionary could contain duplicate long/int keys
if the key value was larger than 2**32. See SF bug #689659.
);
static PyObject *
-sys_exc_info(PyObject *self)
+sys_exc_info(PyObject *self, PyObject *noargs)
{
PyThreadState *tstate;
tstate = PyThreadState_Get();
PyDoc_STRVAR(exc_info_doc,
"exc_info() -> (type, value, traceback)\n\
\n\
-Return information about the exception that is currently being handled.\n\
-This should be called from inside an except clause only."
+Return information about the most recent exception caught by an except\n\
+clause in the current stack frame or in an older stack frame."
+);
+
+static PyObject *
+sys_exc_clear(PyObject *self, PyObject *noargs)
+{
+ PyThreadState *tstate = PyThreadState_Get();
+ PyObject *tmp_type, *tmp_value, *tmp_tb;
+ tmp_type = tstate->exc_type;
+ tmp_value = tstate->exc_value;
+ tmp_tb = tstate->exc_traceback;
+ tstate->exc_type = NULL;
+ tstate->exc_value = NULL;
+ tstate->exc_traceback = NULL;
+ Py_XDECREF(tmp_type);
+ Py_XDECREF(tmp_value);
+ Py_XDECREF(tmp_tb);
+ /* For b/w compatibility */
+ PySys_SetObject("exc_type", Py_None);
+ PySys_SetObject("exc_value", Py_None);
+ PySys_SetObject("exc_traceback", Py_None);
+ Py_INCREF(Py_None);
+ return Py_None;
+}
+
+PyDoc_STRVAR(exc_clear_doc,
+"exc_clear() -> None\n\
+\n\
+Clear global information on the current exception. Subsequent calls to\n\
+exc_info() will return (None,None,None) until another exception is raised\n\
+in the current thread or the execution stack returns to a frame where\n\
+another exception is being handled."
);
static PyObject *
{"callstats", (PyCFunction)PyEval_GetCallStats, METH_NOARGS,
callstats_doc},
{"displayhook", sys_displayhook, METH_O, displayhook_doc},
- {"exc_info", (PyCFunction)sys_exc_info, METH_NOARGS, exc_info_doc},
+ {"exc_info", sys_exc_info, METH_NOARGS, exc_info_doc},
+ {"exc_clear", sys_exc_clear, METH_NOARGS, exc_clear_doc},
{"excepthook", sys_excepthook, METH_VARARGS, excepthook_doc},
{"exit", sys_exit, METH_VARARGS, exit_doc},
#ifdef Py_USING_UNICODE
displayhook() -- print an object to the screen, and save it in __builtin__._\n\
excepthook() -- print an exception and its traceback to sys.stderr\n\
exc_info() -- return thread-safe information about the current exception\n\
+exc_clear() -- clear the exception state for the current thread\n\
exit() -- exit the interpreter by raising SystemExit\n\
getdlopenflags() -- returns flags to be used for dlopen() calls\n\
getrefcount() -- return the reference count for an object (plus one :-)\n\
projects / python / commitdiff