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authorGuido van Rossum <guido@python.org>1999-06-22 14:47:32 (GMT)
committerGuido van Rossum <guido@python.org>1999-06-22 14:47:32 (GMT)
commit87460821755ba72294b0c95b7d130b922d2a7ea4 (patch)
tree0f0a205db4141203afe732f9aeafaeeddaf36386 /Python
parent43128905befc05001219d79715448191a04b8ab9 (diff)
downloadcpython-87460821755ba72294b0c95b7d130b922d2a7ea4.zip
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Patch by Tim Peters:
Introduce a new builtin exception, UnboundLocalError, raised when ceval.c tries to retrieve or delete a local name that isn't bound to a value. Currently raises NameError, which makes this behavior a FAQ since the same error is raised for "missing" global names too: when the user has a global of the same name as the unbound local, NameError makes no sense to them. Even in the absence of shadowing, knowing whether a bogus name is local or global is a real aid to quick understanding. Example: D:\src\PCbuild>type local.py x = 42 def f(): print x x = 13 return x f() D:\src\PCbuild>python local.py Traceback (innermost last): File "local.py", line 8, in ? f() File "local.py", line 4, in f print x UnboundLocalError: x D:\src\PCbuild> Note that UnboundLocalError is a subclass of NameError, for compatibility with existing class-exception code that may be trying to catch this as a NameError. Unfortunately, I see no way to make this wholly compatible with -X (see comments in bltinmodule.c): under -X, [UnboundLocalError is an alias for NameError --GvR]. [The ceval.c patch differs slightly from the second version that Tim submitted; I decided not to raise UnboundLocalError for DELETE_NAME, only for DELETE_LOCAL. DELETE_NAME is only generated at the module level, and since at that level a NameError is raised for referencing an undefined name, it should also be raised for deleting one.]
Diffstat (limited to 'Python')
-rw-r--r--Python/bltinmodule.c15
-rw-r--r--Python/ceval.c4
2 files changed, 17 insertions, 2 deletions
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 3ddf885..4e20eda 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2232,6 +2232,7 @@ PyObject *PyExc_NotImplementedError;
PyObject *PyExc_SyntaxError;
PyObject *PyExc_SystemError;
PyObject *PyExc_SystemExit;
+PyObject *PyExc_UnboundLocalError;
PyObject *PyExc_TypeError;
PyObject *PyExc_ValueError;
PyObject *PyExc_ZeroDivisionError;
@@ -2261,6 +2262,11 @@ bltin_exc[] = {
{"KeyError", &PyExc_KeyError, 1},
{"KeyboardInterrupt", &PyExc_KeyboardInterrupt, 1},
{"MemoryError", &PyExc_MemoryError, 1},
+ /* Note: NameError is not a leaf in exceptions.py, but unlike
+ the other non-leafs NameError is meant to be raised directly
+ at times -- the leaf_exc member really seems to mean something
+ like "this is an abstract base class" when false.
+ */
{"NameError", &PyExc_NameError, 1},
{"OverflowError", &PyExc_OverflowError, 1},
{"RuntimeError", &PyExc_RuntimeError, 1},
@@ -2268,6 +2274,7 @@ bltin_exc[] = {
{"SyntaxError", &PyExc_SyntaxError, 1},
{"SystemError", &PyExc_SystemError, 1},
{"SystemExit", &PyExc_SystemExit, 1},
+ {"UnboundLocalError", &PyExc_UnboundLocalError, 1},
{"TypeError", &PyExc_TypeError, 1},
{"ValueError", &PyExc_ValueError, 1},
{"ZeroDivisionError", &PyExc_ZeroDivisionError, 1},
@@ -2420,6 +2427,14 @@ initerrors(dict)
PyTuple_SET_ITEM(PyExc_EnvironmentError, 1, PyExc_OSError);
PyDict_SetItemString(dict, "EnvironmentError", PyExc_EnvironmentError);
+ /* Make UnboundLocalError an alias for NameError */
+ Py_INCREF(PyExc_NameError);
+ Py_DECREF(PyExc_UnboundLocalError);
+ PyExc_UnboundLocalError = PyExc_NameError;
+ if (PyDict_SetItemString(dict, "UnboundLocalError",
+ PyExc_NameError) != 0)
+ Py_FatalError("Cannot create string-based exceptions");
+
/* missing from the StandardError tuple: Exception, StandardError,
* and SystemExit
*/
diff --git a/Python/ceval.c b/Python/ceval.c
index 6218397..1c51ccf 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1320,7 +1320,7 @@ eval_code2(co, globals, locals,
case LOAD_FAST:
x = GETLOCAL(oparg);
if (x == NULL) {
- PyErr_SetObject(PyExc_NameError,
+ PyErr_SetObject(PyExc_UnboundLocalError,
PyTuple_GetItem(co->co_varnames,
oparg));
break;
@@ -1338,7 +1338,7 @@ eval_code2(co, globals, locals,
case DELETE_FAST:
x = GETLOCAL(oparg);
if (x == NULL) {
- PyErr_SetObject(PyExc_NameError,
+ PyErr_SetObject(PyExc_UnboundLocalError,
PyTuple_GetItem(co->co_varnames,
oparg));
break;