Generalize tuple() to work nicely with iterators.
NEEDS DOC CHANGES.
This one surprised me! While I expected tuple() to be a no-brainer, turns
out it's actually dripping with consequences:
1. It will *allow* the popular PySequence_Fast() to work with any iterable
object (code for that not yet checked in, but should be trivial).
2. It caused two std tests to fail. This because some places used
PyTuple_Sequence() (the C spelling of tuple()) as an indirect way to test
whether something *is* a sequence. But tuple() code only looked for the
existence of sq->item to determine that, and e.g. an instance passed
that test whether or not it supported the other operations tuple()
needed (e.g., __len__). So some things the tests *expected* to fail
with an AttributeError now fail with a TypeError instead. This looks
like an improvement to me; e.g., test_coercion used to produce 559
TypeErrors and 2 AttributeErrors, and now they're all TypeErrors. The
error details are more informative too, because the places calling this
were *looking* for TypeErrors in order to replace the generic tuple()
"not a sequence" msg with their own more specific text, and
AttributeErrors snuck by that.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index 7133867..2fe6b1f 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -1176,61 +1176,68 @@
PyObject *
PySequence_Tuple(PyObject *v)
{
- PySequenceMethods *m;
+ PyObject *it; /* iter(v) */
+ int n; /* guess for result tuple size */
+ PyObject *result;
+ int j;
if (v == NULL)
return null_error();
+ /* Special-case the common tuple and list cases, for efficiency. */
if (PyTuple_Check(v)) {
Py_INCREF(v);
return v;
}
-
if (PyList_Check(v))
return PyList_AsTuple(v);
- /* There used to be code for strings here, but tuplifying strings is
- not a common activity, so I nuked it. Down with code bloat! */
+ /* Get iterator. */
+ it = PyObject_GetIter(v);
+ if (it == NULL)
+ return type_error("tuple() argument must support iteration");
- /* Generic sequence object */
- m = v->ob_type->tp_as_sequence;
- if (m && m->sq_item) {
- int i;
- PyObject *t;
- int n = PySequence_Size(v);
- if (n < 0)
- return NULL;
- t = PyTuple_New(n);
- if (t == NULL)
- return NULL;
- for (i = 0; ; i++) {
- PyObject *item = (*m->sq_item)(v, i);
- if (item == NULL) {
- if (PyErr_ExceptionMatches(PyExc_IndexError))
- PyErr_Clear();
- else {
- Py_DECREF(t);
- t = NULL;
- }
- break;
- }
- if (i >= n) {
- if (n < 500)
- n += 10;
- else
- n += 100;
- if (_PyTuple_Resize(&t, n, 0) != 0)
- break;
- }
- PyTuple_SET_ITEM(t, i, item);
+ /* Guess result size and allocate space. */
+ n = PySequence_Size(v);
+ if (n < 0) {
+ PyErr_Clear();
+ n = 10; /* arbitrary */
+ }
+ result = PyTuple_New(n);
+ if (result == NULL)
+ goto Fail;
+
+ /* Fill the tuple. */
+ for (j = 0; ; ++j) {
+ PyObject *item = PyIter_Next(it);
+ if (item == NULL) {
+ if (PyErr_Occurred())
+ goto Fail;
+ break;
}
- if (i < n && t != NULL)
- _PyTuple_Resize(&t, i, 0);
- return t;
+ if (j >= n) {
+ if (n < 500)
+ n += 10;
+ else
+ n += 100;
+ if (_PyTuple_Resize(&result, n, 0) != 0)
+ goto Fail;
+ }
+ PyTuple_SET_ITEM(result, j, item);
}
- /* None of the above */
- return type_error("tuple() argument must be a sequence");
+ /* Cut tuple back if guess was too large. */
+ if (j < n &&
+ _PyTuple_Resize(&result, j, 0) != 0)
+ goto Fail;
+
+ Py_DECREF(it);
+ return result;
+
+Fail:
+ Py_XDECREF(result);
+ Py_DECREF(it);
+ return NULL;
}
PyObject *