mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-04 00:48:58 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 8

Issue #1766304: Optimize membership testing for ranges: 'n in range(...)'

Browse source 
does an O(1) check, if n is an integer.  Non-integers aren't affected.
Thanks Robert Lehmann.
This commit is contained in:
Mark Dickinson 2009-09-22 21:47:24 +00:00
parent 2df8113622
commit 3e124ae739
4 changed files with 113 additions and 0 deletions
Download patch file Download diff file Expand all files Collapse all files

57
Objects/rangeobject.c
View file

@ -273,12 +273,69 @@ range_reduce(rangeobject *r, PyObject *args)
r->start, r->stop, r->step);
}
static int
range_contains(rangeobject *r, PyObject *ob) {
if (PyLong_Check(ob)) {
int cmp1, cmp2, cmp3;
PyObject *tmp1 = NULL;
PyObject *tmp2 = NULL;
PyObject *zero = NULL;
int result = -1;
zero = PyLong_FromLong(0);
if (zero == NULL) /* MemoryError in int(0) */
goto end;
/* Check if the value can possibly be in the range. */
cmp1 = PyObject_RichCompareBool(r->step, zero, Py_GT);
if (cmp1 == -1)
goto end;
if (cmp1 == 1) { /* positive steps: start <= ob < stop */
cmp2 = PyObject_RichCompareBool(r->start, ob, Py_LE);
cmp3 = PyObject_RichCompareBool(ob, r->stop, Py_LT);
}
else { /* negative steps: stop < ob <= start */
cmp2 = PyObject_RichCompareBool(ob, r->start, Py_LE);
cmp3 = PyObject_RichCompareBool(r->stop, ob, Py_LT);
}
if (cmp2 == -1 || cmp3 == -1) /* TypeError */
goto end;
if (cmp2 == 0 || cmp3 == 0) { /* ob outside of range */
result = 0;
goto end;
}
/* Check that the stride does not invalidate ob's membership. */
tmp1 = PyNumber_Subtract(ob, r->start);
if (tmp1 == NULL)
goto end;
tmp2 = PyNumber_Remainder(tmp1, r->step);
if (tmp2 == NULL)
goto end;
/* result = (int(ob) - start % step) == 0 */
result = PyObject_RichCompareBool(tmp2, zero, Py_EQ);
end:
Py_XDECREF(tmp1);
Py_XDECREF(tmp2);
Py_XDECREF(zero);
return result;
}
/* Fall back to iterative search. */
return (int)_PySequence_IterSearch((PyObject*)r, ob,
PY_ITERSEARCH_CONTAINS);
}
static PySequenceMethods range_as_sequence = {
(lenfunc)range_length, /* sq_length */
0, /* sq_concat */
0, /* sq_repeat */
(ssizeargfunc)range_item, /* sq_item */
0, /* sq_slice */
0, /* sq_ass_item */
0, /* sq_ass_slice */
(objobjproc)range_contains, /* sq_contains */
};
static PyObject * range_iter(PyObject *seq);