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Issue 5032: added a step argument to itertools.count() and allowed non-integer arguments.

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This commit is contained in:
Raymond Hettinger 2009-02-12 06:28:27 +00:00
parent a9cab51965
commit 3072921d0e
4 changed files with 133 additions and 41 deletions
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114
Modules/itertoolsmodule.c
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@ -2886,9 +2886,27 @@ static PyTypeObject filterfalse_type = {
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 *
@ -2896,28 +2914,45 @@ count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
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 = PyLong_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 = 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 */
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);
@ -2927,6 +2962,7 @@ count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
}
lz->cnt = cnt;
lz->long_cnt = long_cnt;
lz->long_step = long_step;
return (PyObject *)lz;
}
@ -2934,7 +2970,8 @@ count_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
static void
count_dealloc(countobject *lz)
{
Py_XDECREF(lz->long_cnt);
Py_XDECREF(lz->long_cnt);
Py_XDECREF(lz->long_step);
PyObject_Del(lz);
}
@ -2942,32 +2979,29 @@ static PyObject *
count_nextlong(countobject *lz)
{
static PyObject *one = NULL;
PyObject *cnt;
PyObject *long_cnt;
PyObject *stepped_up;
if (lz->long_cnt == NULL) {
lz->long_cnt = PyLong_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 = PyLong_FromSsize_t(PY_SSIZE_T_MAX);
if (long_cnt == NULL)
return NULL;
}
if (one == NULL) {
one = PyLong_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 PyLong_FromSsize_t(lz->cnt++);
}
@ -2975,17 +3009,35 @@ count_next(countobject *lz)
static PyObject *
count_repr(countobject *lz)
{
if (lz->cnt != PY_SSIZE_T_MAX)
if (lz->cnt != PY_SSIZE_T_MAX)
return PyUnicode_FromFormat("count(%zd)", lz->cnt);
return PyUnicode_FromFormat("count(%R)", lz->long_cnt);
if (PyLong_Check(lz->long_step)) {
long step = PyLong_AsLong(lz->long_step);
if (step == -1 && PyErr_Occurred()) {
PyErr_Clear();
}
if (step == 1) {
/* Don't display step when it is an integer equal to 1 */
return PyUnicode_FromFormat("count(%R)", lz->long_cnt);
}
}
return PyUnicode_FromFormat("count(%R, %R)",
lz->long_cnt, lz->long_step);
}
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)