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Port r69837: Fix keyword arguments for itertools.count(). Step arg without a start arg was ignored.

This commit is contained in:
Raymond Hettinger 2009-02-21 22:30:12 +00:00
parent bd171bcfc4
commit eb13fdda59
2 changed files with 50 additions and 31 deletions
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4
Lib/test/test_itertools.py
View File

@ -354,6 +354,10 @@ class TestBasicOps(unittest.TestCase):
def test_count_with_stride(self):
self.assertEqual(lzip('abc',count(2,3)), [('a', 2), ('b', 5), ('c', 8)])
self.assertEqual(lzip('abc',count(start=2,step=3)),
[('a', 2), ('b', 5), ('c', 8)])
self.assertEqual(lzip('abc',count(step=-1)),
[('a', 0), ('b', -1), ('c', -2)])
self.assertEqual(lzip('abc',count(2,0)), [('a', 2), ('b', 2), ('c', 2)])
self.assertEqual(lzip('abc',count(2,1)), [('a', 2), ('b', 3), ('c', 4)])
self.assertEqual(lzip('abc',count(2,3)), [('a', 2), ('b', 5), ('c', 8)])

77
Modules/itertoolsmodule.c
View File

@ -2892,19 +2892,19 @@ typedef struct {
/* Counting logic and invariants:
C_add_mode: when cnt an integer < PY_SSIZE_T_MAX and no step is specified.
fast_mode: when cnt an integer < PY_SSIZE_T_MAX and no step is specified.
assert(cnt != PY_SSIZE_T_MAX && long_cnt == NULL && long_step==PyInt(1));
Advances with: cnt += 1
When count hits Y_SSIZE_T_MAX, switch to Py_add_mode.
When count hits Y_SSIZE_T_MAX, switch to slow_mode.
Py_add_mode: when cnt == PY_SSIZE_T_MAX, step is not int(1), or cnt is a float.
slow_mode: when cnt == PY_SSIZE_T_MAX, step is not int(1), or cnt is a float.
assert(cnt == PY_SSIZE_T_MAX && long_cnt != NULL && long_step != NULL);
All counting is done with python objects (no overflows or underflows).
Advances with: long_cnt += long_step
Step may be zero -- effectively a slow version of repeat(cnt).
Either long_cnt or long_step may be a float.
Either long_cnt or long_step may be a float, Fraction, or Decimal.
*/
static PyTypeObject count_type;
@ -2913,6 +2913,7 @@ static PyObject *
count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
countobject *lz;
int slow_mode = 0;
Py_ssize_t cnt = 0;
PyObject *long_cnt = NULL;
PyObject *long_step = NULL;
@ -2922,36 +2923,51 @@ count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
kwlist, &long_cnt, &long_step))
return NULL;
if ((long_cnt != NULL && !PyNumber_Check(long_cnt)) ||
(long_step != NULL && !PyNumber_Check(long_step))) {
if (long_cnt != NULL && !PyNumber_Check(long_cnt) ||
long_step != NULL && !PyNumber_Check(long_step)) {
PyErr_SetString(PyExc_TypeError, "a number is required");
return NULL;
}
if (long_step == NULL) {
/* If not specified, step defaults to 1 */
long_step = PyLong_FromLong(1);
if (long_step == NULL)
return NULL;
} else
Py_INCREF(long_step);
assert(long_step != NULL);
if (long_cnt != NULL) {
cnt = PyLong_AsSsize_t(long_cnt);
if ((cnt == -1 && PyErr_Occurred()) ||
!PyIndex_Check(long_cnt) ||
!PyLong_Check(long_step) ||
PyLong_AS_LONG(long_step) != 1) {
/* Switch to Py_add_mode */
if (cnt == -1 && PyErr_Occurred() || !PyLong_Check(long_cnt)) {
PyErr_Clear();
Py_INCREF(long_cnt);
cnt = PY_SSIZE_T_MAX;
} else
long_cnt = NULL;
slow_mode = 1;
}
Py_INCREF(long_cnt);
} else {
cnt = 0;
long_cnt = PyLong_FromLong(0);
}
assert((cnt != PY_SSIZE_T_MAX && long_cnt == NULL) ||
(cnt == PY_SSIZE_T_MAX && long_cnt != NULL));
/* If not specified, step defaults to 1 */
if (long_step == NULL) {
long_step = PyLong_FromLong(1);
if (long_step == NULL) {
Py_DECREF(long_cnt);
return NULL;
}
} else
Py_INCREF(long_step);
assert(long_cnt != NULL && long_step != NULL);
/* Fast mode only works when the step is 1 */
if (!PyLong_Check(long_step) ||
PyLong_AS_LONG(long_step) != 1) {
slow_mode = 1;
}
if (slow_mode)
cnt = PY_SSIZE_T_MAX;
else
Py_CLEAR(long_cnt);
assert(cnt != PY_SSIZE_T_MAX && long_cnt == NULL && !slow_mode ||
cnt == PY_SSIZE_T_MAX && long_cnt != NULL && slow_mode);
assert(slow_mode ||
PyLong_Check(long_step) && PyLong_AS_LONG(long_step) == 1);
/* create countobject structure */
lz = (countobject *)type->tp_alloc(type, 0);
@ -2991,7 +3007,7 @@ count_nextlong(countobject *lz)
long_cnt = lz->long_cnt;
if (long_cnt == NULL) {
/* Switch to Py_add_mode */
/* Switch to slow_mode */
long_cnt = PyLong_FromSsize_t(PY_SSIZE_T_MAX);
if (long_cnt == NULL)
return NULL;
@ -3034,11 +3050,10 @@ count_repr(countobject *lz)
}
PyDoc_STRVAR(count_doc,
"count([start[, step]]) --> count object\n\
"count(start=0, step=1]) --> count object\n\
\n\
Return a count object whose .__next__() method returns consecutive\n\
integers starting from zero or, if specified, from start.\n\
If step is specified, counts by that interval. Equivalent to:\n\n\
Return a count object whose .__next__() method returns consecutive values.\n\
Equivalent to:\n\n\
def count(firstval=0, step=1):\n\
x = firstval\n\
while 1:\n\