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Generalize filter(f, seq) to work with iterators. This also generalizes

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filter() to no longer insist that len(seq) be defined.
NEEDS DOC CHANGES.
This commit is contained in:
Tim Peters 2001-05-02 07:39:38 +00:00
parent 6ad22c41c2
commit 0e57abf0cd
3 changed files with 109 additions and 50 deletions
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98
Python/bltinmodule.c
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@ -162,53 +162,65 @@ Note that classes are callable, as are instances with a __call__() method.";
static PyObject *
builtin_filter(PyObject *self, PyObject *args)
{
PyObject *func, *seq, *result;
PySequenceMethods *sqf;
int len;
PyObject *func, *seq, *result, *it;
int len; /* guess for result list size */
register int i, j;
if (!PyArg_ParseTuple(args, "OO:filter", &func, &seq))
return NULL;
if (PyString_Check(seq)) {
PyObject *r = filterstring(func, seq);
return r;
/* Strings and tuples return a result of the same type. */
if (PyString_Check(seq))
return filterstring(func, seq);
if (PyTuple_Check(seq))
return filtertuple(func, seq);
/* Get iterator. */
it = PyObject_GetIter(seq);
if (it == NULL)
return NULL;
/* Guess a result list size. */
len = -1; /* unknown */
if (PySequence_Check(seq) &&
seq->ob_type->tp_as_sequence->sq_length) {
len = PySequence_Size(seq);
if (len < 0)
PyErr_Clear();
}
if (len < 0)
len = 8; /* arbitrary */
if (PyTuple_Check(seq)) {
PyObject *r = filtertuple(func, seq);
return r;
}
sqf = seq->ob_type->tp_as_sequence;
if (sqf == NULL || sqf->sq_length == NULL || sqf->sq_item == NULL) {
PyErr_SetString(PyExc_TypeError,
"filter() arg 2 must be a sequence");
goto Fail_2;
}
if ((len = (*sqf->sq_length)(seq)) < 0)
goto Fail_2;
/* Get a result list. */
if (PyList_Check(seq) && seq->ob_refcnt == 1) {
/* Eww - can modify the list in-place. */
Py_INCREF(seq);
result = seq;
}
else {
if ((result = PyList_New(len)) == NULL)
goto Fail_2;
result = PyList_New(len);
if (result == NULL)
goto Fail_it;
}
/* Build the result list. */
for (i = j = 0; ; ++i) {
PyObject *item, *good;
int ok;
if ((item = (*sqf->sq_item)(seq, i)) == NULL) {
if (PyErr_ExceptionMatches(PyExc_IndexError)) {
PyErr_Clear();
break;
item = PyIter_Next(it);
if (item == NULL) {
/* We're out of here in any case, but if this is a
* StopIteration exception it's expected, but if
* any other kind of exception it's an error.
*/
if (PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
else
goto Fail_result_it;
}
goto Fail_1;
break;
}
if (func == Py_None) {
@ -217,43 +229,45 @@ builtin_filter(PyObject *self, PyObject *args)
}
else {
PyObject *arg = Py_BuildValue("(O)", item);
if (arg == NULL)
goto Fail_1;
if (arg == NULL) {
Py_DECREF(item);
goto Fail_result_it;
}
good = PyEval_CallObject(func, arg);
Py_DECREF(arg);
if (good == NULL) {
Py_DECREF(item);
goto Fail_1;
goto Fail_result_it;
}
}
ok = PyObject_IsTrue(good);
Py_DECREF(good);
if (ok) {
if (j < len) {
if (PyList_SetItem(result, j++, item) < 0)
goto Fail_1;
}
if (j < len)
PyList_SET_ITEM(result, j, item);
else {
int status = PyList_Append(result, item);
j++;
Py_DECREF(item);
if (status < 0)
goto Fail_1;
goto Fail_result_it;
}
} else {
Py_DECREF(item);
++j;
}
else
Py_DECREF(item);
}
/* Cut back result list if len is too big. */
if (j < len && PyList_SetSlice(result, j, len, NULL) < 0)
goto Fail_1;
goto Fail_result_it;
return result;
Fail_1:
Fail_result_it:
Py_DECREF(result);
Fail_2:
Fail_it:
Py_DECREF(it);
return NULL;
}