Skip to content

bpo-29312: use METH_FASTCALL for dict.update #14589

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 1 commit into from
Closed

bpo-29312: use METH_FASTCALL for dict.update #14589

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
4 changes: 3 additions & 1 deletion Lib/test/test_dict.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -142,9 +142,11 @@ def test_update(self):
d.update({2:20})
d.update({1:1, 2:2, 3:3})
self.assertEqual(d, {1:1, 2:2, 3:3})
d.update(([i,i] for i in range(4,6)), key="value")
self.assertEqual(d, {1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 'key': 'value'})

d.update()
self.assertEqual(d, {1:1, 2:2, 3:3})
self.assertEqual(d, {1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 'key': 'value'})

self.assertRaises((TypeError, AttributeError), d.update, None)

Expand Down
106 changes: 95 additions & 11 deletions Objects/dictobject.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -2340,16 +2340,6 @@ dict_update_common(PyObject *self, PyObject *args, PyObject *kwds,
return result;
}

/* Note: dict.update() uses the METH_VARARGS|METH_KEYWORDS calling convention.
Using METH_FASTCALL|METH_KEYWORDS would make dict.update(**dict2) calls
slower, see the issue #29312. */
static PyObject *
dict_update(PyObject *self, PyObject *args, PyObject *kwds)
{
if (dict_update_common(self, args, kwds, "update") != -1)
Py_RETURN_NONE;
return NULL;
}

/* Update unconditionally replaces existing items.
Merge has a 3rd argument 'override'; if set, it acts like Update,
Expand Down Expand Up @@ -2591,6 +2581,100 @@ dict_merge(PyObject *a, PyObject *b, int override)
return 0;
}

/* Implementation of d.update(obj). There are two cases:
* - if obj has a "keys" method, assume that it is a mapping
* - otherwise, obj must be an iterable of (key, value) pairs
*/
static int
dict_merge_from_any(PyObject *self, PyObject *obj)
{
/* Fast path for dict subclasses */
if (PyDict_Check(obj)) {
return dict_merge(self, obj, 1);
}

_Py_IDENTIFIER(keys);
PyObject *func;
if (_PyObject_LookupAttrId(obj, &PyId_keys, &func) < 0) {
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

That sounds redundant with dict_merge() which calls PyMapping_Keys(). Maybe dict_merge() could be modified to dispatch to PyDict_MergeFromSeq2() if PyMapping_Keys() keys with an attribute error, rather than trying to get the attribute twice?

It's not directly related to your change, it can be done/discussed in a separated PR.

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I agree, I also noticed this. There is some room for improvement here. Let's do it in a new PR after this is merged.

return -1;
}
if (func != NULL) {
Py_DECREF(func);
return dict_merge(self, obj, 1);
}
else {
return PyDict_MergeFromSeq2(self, obj, 1);
}
}

/* Insert the key:value pairs from the arrays keys and values (of length n).
* Return 0 if successful, -1 if an exception was raised */
static int
dict_merge_from_arrays(PyDictObject *mp, PyObject *const *keys, PyObject *const *values, Py_ssize_t n)
{
/* Do one big resize at the start, rather than
* incrementally resizing as we insert new items. Expect
* that there will be no (or few) overlapping keys.
*/
if (USABLE_FRACTION(mp->ma_keys->dk_size) < n) {
if (dictresize(mp, ESTIMATE_SIZE(mp->ma_used + n))) {
return -1;
}
}

for (Py_ssize_t i = 0; i < n; i++) {
PyObject *key = keys[i];
PyObject *value = values[i];
assert(PyUnicode_Check(key));
Py_hash_t hash = ((PyASCIIObject *)key)->hash;
if (hash == -1) {
hash = PyObject_Hash(key);
if (hash == -1) {
return -1;
}
}
if (insertdict(mp, key, hash, value)) {
return -1;
}
}
ASSERT_CONSISTENT(mp);
return 0;
}


static int
dict_update_impl(PyObject *self, PyObject *const *args,
Py_ssize_t nargs, PyObject *kwnames,
const char *methname)
{
if (nargs) {
if (!_PyArg_CheckPositional(methname, nargs, 0, 1)) {
return -1;
}
if (dict_merge_from_any(self, args[0])) {
return -1;
}
args += 1;
}
if (kwnames) {
Py_ssize_t nkw = PyTuple_GET_SIZE(kwnames);
PyObject *const *names = &PyTuple_GET_ITEM(kwnames, 0);
return dict_merge_from_arrays((PyDictObject*)self, names, args, nkw);
}
return 0;
}

static PyObject *
dict_update(PyObject *self, PyObject *const *args,
Py_ssize_t nargs, PyObject *kwnames)
{
if (dict_update_impl(self, args, nargs, kwnames, "update")) {
return NULL;
}
Py_RETURN_NONE;
}


int
PyDict_Update(PyObject *a, PyObject *b)
{
Expand Down Expand Up @@ -3193,7 +3277,7 @@ static PyMethodDef mapp_methods[] = {
items__doc__},
{"values", dictvalues_new, METH_NOARGS,
values__doc__},
{"update", (PyCFunction)(void(*)(void))dict_update, METH_VARARGS | METH_KEYWORDS,
{"update", (PyCFunction)(void(*)(void))dict_update, METH_FASTCALL | METH_KEYWORDS,
update__doc__},
DICT_FROMKEYS_METHODDEF
{"clear", (PyCFunction)dict_clear, METH_NOARGS,
Expand Down