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gh-110067: Optimize nlargest/nsmallest and improve max-heap C docstrings #146168

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gh-110067: Optimize nlargest/nsmallest and improve max-heap C docstrings #146168

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8 changes: 8 additions & 0 deletions Lib/heapq.py
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Original file line number Diff line number Diff line change
Expand Up @@ -480,6 +480,10 @@ def nsmallest(n, iterable, key=None):
Equivalent to: sorted(iterable, key=key)[:n]
"""

# Short-cut for n<=0 to avoid unnecessary work
if n <= 0:
return []

# Short-cut for n==1 is to use min()
if n == 1:
it = iter(iterable)
Expand Down Expand Up @@ -540,6 +544,10 @@ def nlargest(n, iterable, key=None):
Equivalent to: sorted(iterable, key=key, reverse=True)[:n]
"""

# Short-cut for n<=0 to avoid unnecessary work
if n <= 0:
return []

# Short-cut for n==1 is to use max()
if n == 1:
it = iter(iterable)
Expand Down
3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Library/2026-03-19-00-00-00.gh-issue-110067.RWJ5vA7m.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Add early return for ``n <= 0`` in :func:`heapq.nsmallest` and
:func:`heapq.nlargest`, and improve docstrings for :func:`heapq.heappop_max`,
:func:`heapq.heapreplace_max`, and :func:`heapq.heapify_max`.
15 changes: 8 additions & 7 deletions Modules/_heapqmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -424,7 +424,8 @@ siftdown_max(PyListObject *heap, Py_ssize_t startpos, Py_ssize_t pos)
newitem = arr[pos];
while (pos > startpos) {
parentpos = (pos - 1) >> 1;
parent = Py_NewRef(arr[parentpos]);
parent = arr[parentpos];
Py_INCREF(parent);
Py_INCREF(newitem);
cmp = PyObject_RichCompareBool(parent, newitem, Py_LT);
Py_DECREF(parent);
Expand Down Expand Up @@ -538,12 +539,12 @@ _heapq.heappop_max
heap: object(subclass_of='&PyList_Type')
/

Maxheap variant of heappop.
Pop the largest item off the max-heap, maintaining the heap invariant.
[clinic start generated code]*/

static PyObject *
_heapq_heappop_max_impl(PyObject *module, PyObject *heap)
/*[clinic end generated code: output=2f051195ab404b77 input=5d70c997798aec64]*/
/*[clinic end generated code: output=2f051195ab404b77 input=edca3ff5d6aa11c6]*/
{
return heappop_internal(heap, siftup_max);
}
Expand All @@ -556,12 +557,12 @@ _heapq.heapreplace_max
item: object
/

Maxheap variant of heapreplace.
Pop and return the largest item from the max-heap, and push the new item.
[clinic start generated code]*/

static PyObject *
_heapq_heapreplace_max_impl(PyObject *module, PyObject *heap, PyObject *item)
/*[clinic end generated code: output=8770778b5a9cbe9b input=fe70175356e4a649]*/
/*[clinic end generated code: output=8770778b5a9cbe9b input=75b704b6f92beab9]*/
{
return heapreplace_internal(heap, item, siftup_max);
}
Expand All @@ -573,12 +574,12 @@ _heapq.heapify_max
heap: object(subclass_of='&PyList_Type')
/

Maxheap variant of heapify.
Transform list into a max-heap, in-place, in O(len(heap)) time.
[clinic start generated code]*/

static PyObject *
_heapq_heapify_max_impl(PyObject *module, PyObject *heap)
/*[clinic end generated code: output=8401af3856529807 input=4eee63231e7d1573]*/
/*[clinic end generated code: output=8401af3856529807 input=4e02ed8aa546fb8e]*/
{
return heapify_internal(heap, siftup_max);
}
Expand Down
8 changes: 4 additions & 4 deletions Modules/clinic/_heapqmodule.c.h
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