Issue 5032: added a step argument to itertools.count() and allowed non-integer arguments.
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 486c2e0..aa764d8 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -3203,9 +3203,27 @@
typedef struct {
PyObject_HEAD
Py_ssize_t cnt;
- PyObject *long_cnt; /* Arbitrarily large count when cnt >= PY_SSIZE_T_MAX */
+ PyObject *long_cnt;
+ PyObject *long_step;
} countobject;
+/* Counting logic and invariants:
+
+C_add_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.
+
+Py_add_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.
+*/
+
static PyTypeObject count_type;
static PyObject *
@@ -3213,28 +3231,45 @@
{
countobject *lz;
Py_ssize_t cnt = 0;
- PyObject *cnt_arg = NULL;
PyObject *long_cnt = NULL;
+ PyObject *long_step = NULL;
if (type == &count_type && !_PyArg_NoKeywords("count()", kwds))
return NULL;
- if (!PyArg_UnpackTuple(args, "count", 0, 1, &cnt_arg))
+ if (!PyArg_UnpackTuple(args, "count", 0, 2, &long_cnt, &long_step))
return NULL;
- if (cnt_arg != NULL) {
- cnt = PyInt_AsSsize_t(cnt_arg);
- if (cnt == -1 && PyErr_Occurred()) {
+ 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 = PyInt_FromLong(1);
+ if (long_step == NULL)
+ return NULL;
+ } else
+ Py_INCREF(long_step);
+ assert(long_step != NULL);
+
+ if (long_cnt != NULL) {
+ cnt = PyInt_AsSsize_t(long_cnt);
+ if ((cnt == -1 && PyErr_Occurred()) ||
+ !PyIndex_Check(long_cnt) ||
+ !PyInt_Check(long_step) ||
+ PyInt_AS_LONG(long_step) != 1) {
+ /* Switch to Py_add_mode */
PyErr_Clear();
- if (!PyLong_Check(cnt_arg)) {
- PyErr_SetString(PyExc_TypeError, "an integer is required");
- return NULL;
- }
- long_cnt = cnt_arg;
Py_INCREF(long_cnt);
cnt = PY_SSIZE_T_MAX;
- }
+ } else
+ long_cnt = NULL;
}
+ assert(cnt != PY_SSIZE_T_MAX && long_cnt == NULL ||
+ cnt == PY_SSIZE_T_MAX && long_cnt != NULL);
/* create countobject structure */
lz = (countobject *)PyObject_New(countobject, &count_type);
@@ -3244,6 +3279,7 @@
}
lz->cnt = cnt;
lz->long_cnt = long_cnt;
+ lz->long_step = long_step;
return (PyObject *)lz;
}
@@ -3251,7 +3287,8 @@
static void
count_dealloc(countobject *lz)
{
- Py_XDECREF(lz->long_cnt);
+ Py_XDECREF(lz->long_cnt);
+ Py_XDECREF(lz->long_step);
PyObject_Del(lz);
}
@@ -3259,32 +3296,29 @@
count_nextlong(countobject *lz)
{
static PyObject *one = NULL;
- PyObject *cnt;
+ PyObject *long_cnt;
PyObject *stepped_up;
- if (lz->long_cnt == NULL) {
- lz->long_cnt = PyInt_FromSsize_t(PY_SSIZE_T_MAX);
- if (lz->long_cnt == NULL)
+ long_cnt = lz->long_cnt;
+ if (long_cnt == NULL) {
+ /* Switch to Py_add_mode */
+ long_cnt = PyInt_FromSsize_t(PY_SSIZE_T_MAX);
+ if (long_cnt == NULL)
return NULL;
}
- if (one == NULL) {
- one = PyInt_FromLong(1);
- if (one == NULL)
- return NULL;
- }
- cnt = lz->long_cnt;
- assert(cnt != NULL);
- stepped_up = PyNumber_Add(cnt, one);
+ assert(lz->cnt == PY_SSIZE_T_MAX && long_cnt != NULL);
+
+ stepped_up = PyNumber_Add(long_cnt, lz->long_step);
if (stepped_up == NULL)
return NULL;
lz->long_cnt = stepped_up;
- return cnt;
+ return long_cnt;
}
static PyObject *
count_next(countobject *lz)
{
- if (lz->cnt == PY_SSIZE_T_MAX)
+ if (lz->cnt == PY_SSIZE_T_MAX)
return count_nextlong(lz);
return PyInt_FromSsize_t(lz->cnt++);
}
@@ -3292,25 +3326,44 @@
static PyObject *
count_repr(countobject *lz)
{
- PyObject *cnt_repr;
- PyObject *result;
+ PyObject *cnt_repr, *step_repr = NULL;
+ PyObject *result = NULL;
- if (lz->cnt != PY_SSIZE_T_MAX)
+ if (lz->cnt != PY_SSIZE_T_MAX)
return PyString_FromFormat("count(%zd)", lz->cnt);
cnt_repr = PyObject_Repr(lz->long_cnt);
if (cnt_repr == NULL)
return NULL;
- result = PyString_FromFormat("count(%s)", PyString_AS_STRING(cnt_repr));
+
+ if (PyInt_Check(lz->long_step) && PyInt_AS_LONG(lz->long_step) == 1) {
+ /* Don't display step when it is an integer equal to 1 */
+ result = PyString_FromFormat("count(%s)",
+ PyString_AS_STRING(cnt_repr));
+ } else {
+ step_repr = PyObject_Repr(lz->long_step);
+ if (step_repr != NULL)
+ result = PyString_FromFormat("count(%s, %s)",
+ PyString_AS_STRING(cnt_repr),
+ PyString_AS_STRING(step_repr));
+ }
Py_DECREF(cnt_repr);
+ Py_XDECREF(step_repr);
return result;
}
PyDoc_STRVAR(count_doc,
-"count([firstval]) --> count object\n\
+ "count([firstval[, step]]) --> count object\n\
\n\
Return a count object whose .next() method returns consecutive\n\
-integers starting from zero or, if specified, from firstval.");
+integers starting from zero or, if specified, from firstval.\n\
+If step is specified, counts by that interval.\n\
+Same as:\n\
+ def count(firstval=0, step=1):\n\
+ x = firstval\n\
+ while 1:\n\
+ yield x\n\
+ x += step\n");
static PyTypeObject count_type = {
PyVarObject_HEAD_INIT(NULL, 0)