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author | Guido van Rossum <guido@python.org> | 1999-06-22 14:47:32 (GMT) |
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committer | Guido van Rossum <guido@python.org> | 1999-06-22 14:47:32 (GMT) |
commit | 87460821755ba72294b0c95b7d130b922d2a7ea4 (patch) | |
tree | 0f0a205db4141203afe732f9aeafaeeddaf36386 /Python | |
parent | 43128905befc05001219d79715448191a04b8ab9 (diff) | |
download | cpython-87460821755ba72294b0c95b7d130b922d2a7ea4.zip cpython-87460821755ba72294b0c95b7d130b922d2a7ea4.tar.gz cpython-87460821755ba72294b0c95b7d130b922d2a7ea4.tar.bz2 |
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.c | 15 | ||||
-rw-r--r-- | Python/ceval.c | 4 |
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; |