Generalize filter(f, seq) to work with iterators. This also generalizes
filter() to no longer insist that len(seq) be defined.
NEEDS DOC CHANGES.
diff --git a/Lib/test/test_iter.py b/Lib/test/test_iter.py
index 5b9bf65..952ab66 100644
--- a/Lib/test/test_iter.py
+++ b/Lib/test/test_iter.py
@@ -275,4 +275,48 @@
except OSError:
pass
+ # Test filter()'s use of iterators.
+ def test_builtin_filter(self):
+ self.assertEqual(filter(None, SequenceClass(5)), range(1, 5))
+ self.assertEqual(filter(None, SequenceClass(0)), [])
+ self.assertEqual(filter(None, ()), ())
+ self.assertEqual(filter(None, "abc"), "abc")
+
+ d = {"one": 1, "two": 2, "three": 3}
+ self.assertEqual(filter(None, d), d.keys())
+
+ self.assertRaises(TypeError, filter, None, list)
+ self.assertRaises(TypeError, filter, None, 42)
+
+ class Boolean:
+ def __init__(self, truth):
+ self.truth = truth
+ def __nonzero__(self):
+ return self.truth
+ True = Boolean(1)
+ False = Boolean(0)
+
+ class Seq:
+ def __init__(self, *args):
+ self.vals = args
+ def __iter__(self):
+ class SeqIter:
+ def __init__(self, vals):
+ self.vals = vals
+ self.i = 0
+ def __iter__(self):
+ return self
+ def next(self):
+ i = self.i
+ self.i = i + 1
+ if i < len(self.vals):
+ return self.vals[i]
+ else:
+ raise StopIteration
+ return SeqIter(self.vals)
+
+ seq = Seq(*([True, False] * 25))
+ self.assertEqual(filter(lambda x: not x, seq), [False]*25)
+ self.assertEqual(filter(lambda x: not x, iter(seq)), [False]*25)
+
run_unittest(TestCase)
diff --git a/Misc/NEWS b/Misc/NEWS
index f121bac..bbd2ac3 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -17,7 +17,8 @@
- The following functions were generalized to work nicely with iterator
arguments:
- list()
+ filter()
+ list()
What's New in Python 2.1 (final)?
@@ -236,7 +237,7 @@
- IDLE: syntax warnings in interactive mode are changed into errors.
- Some improvements to Tools/webchecker (ignore some more URL types,
- follow some more links).
+ follow some more links).
- Brought the Tools/compiler package up to date.
@@ -324,23 +325,23 @@
in Flags and take an extra argument, a PyCompilerFlags *; examples:
PyRun_AnyFileExFlags(), PyRun_InteractiveLoopFlags(). These
variants may be removed in Python 2.2, when nested scopes are
- mandatory.
+ mandatory.
Distutils
- the sdist command now writes a PKG-INFO file, as described in PEP 241,
into the release tree.
-- several enhancements to the bdist_wininst command from Thomas Heller
+- several enhancements to the bdist_wininst command from Thomas Heller
(an uninstaller, more customization of the installer's display)
- from Jack Jansen: added Mac-specific code to generate a dialog for
users to specify the command-line (because providing a command-line with
- MacPython is awkward). Jack also made various fixes for the Mac
+ MacPython is awkward). Jack also made various fixes for the Mac
and the Metrowerks compiler.
-
-- added 'platforms' and 'keywords' to the set of metadata that can be
- specified for a distribution.
+
+- added 'platforms' and 'keywords' to the set of metadata that can be
+ specified for a distribution.
- applied patches from Jason Tishler to make the compiler class work with
Cygwin.
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 8572cc8..1051374 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -162,53 +162,65 @@
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 @@
}
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;
}