From cbdca1407043aeccd4402c88a5d7daefda3ae5a7 Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <b.schoenmaeckers@zanders.eu>
Date: Wed, 29 Jan 2025 10:16:08 +0100
Subject: [PATCH 1/2] Optimize `Iterator::last()` for `PyList` & `PyTuple`

---
 newsfragments/4878.added.md |  1 +
 src/types/list.rs           |  8 ++++++++
 src/types/tuple.rs          | 16 ++++++++++++++++
 3 files changed, 25 insertions(+)
 create mode 100644 newsfragments/4878.added.md

diff --git a/newsfragments/4878.added.md b/newsfragments/4878.added.md
new file mode 100644
index 00000000000..040c6d860e5
--- /dev/null
+++ b/newsfragments/4878.added.md
@@ -0,0 +1 @@
+Optimizes `last` for `BoundListIterator`, `BoundTupleIterator` and `BorrowedTupleIterator`
\ No newline at end of file
diff --git a/src/types/list.rs b/src/types/list.rs
index 76da36d00b9..45a69b93195 100644
--- a/src/types/list.rs
+++ b/src/types/list.rs
@@ -631,6 +631,14 @@ impl<'py> Iterator for BoundListIterator<'py> {
         (len, Some(len))
     }
 
+    #[inline]
+    fn last(mut self) -> Option<Self::Item>
+    where
+        Self: Sized,
+    {
+        self.next_back()
+    }
+
     #[inline]
     #[cfg(all(Py_GIL_DISABLED, not(feature = "nightly")))]
     fn fold<B, F>(mut self, init: B, mut f: F) -> B
diff --git a/src/types/tuple.rs b/src/types/tuple.rs
index 8147b872af5..9880c510aa0 100644
--- a/src/types/tuple.rs
+++ b/src/types/tuple.rs
@@ -375,6 +375,14 @@ impl<'py> Iterator for BoundTupleIterator<'py> {
         let len = self.len();
         (len, Some(len))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<Self::Item>
+    where
+        Self: Sized,
+    {
+        self.next_back()
+    }
 }
 
 impl DoubleEndedIterator for BoundTupleIterator<'_> {
@@ -467,6 +475,14 @@ impl<'a, 'py> Iterator for BorrowedTupleIterator<'a, 'py> {
         let len = self.len();
         (len, Some(len))
     }
+
+    #[inline]
+    fn last(mut self) -> Option<Self::Item>
+    where
+        Self: Sized,
+    {
+        self.next_back()
+    }
 }
 
 impl DoubleEndedIterator for BorrowedTupleIterator<'_, '_> {

From 8bc30f93b7d1166b5ad2be464e08497cd49f6070 Mon Sep 17 00:00:00 2001
From: Bas Schoenmaeckers <b.schoenmaeckers@zanders.eu>
Date: Wed, 29 Jan 2025 11:01:44 +0100
Subject: [PATCH 2/2] Optimize `Iterator::count()` for `PyDict`, `PyList`,
 `PyTuple` & `PySet`

---
 newsfragments/4878.added.md |  3 ++-
 src/types/dict.rs           | 16 ++++++++++++++++
 src/types/frozenset.rs      |  8 ++++++++
 src/types/list.rs           |  8 ++++++++
 src/types/set.rs            |  8 ++++++++
 src/types/tuple.rs          | 16 ++++++++++++++++
 6 files changed, 58 insertions(+), 1 deletion(-)

diff --git a/newsfragments/4878.added.md b/newsfragments/4878.added.md
index 040c6d860e5..0130b2b805b 100644
--- a/newsfragments/4878.added.md
+++ b/newsfragments/4878.added.md
@@ -1 +1,2 @@
-Optimizes `last` for `BoundListIterator`, `BoundTupleIterator` and `BorrowedTupleIterator`
\ No newline at end of file
+- Optimizes `last` for `BoundListIterator`, `BoundTupleIterator` and `BorrowedTupleIterator`
+- Optimizes `Iterator::count()` for `PyDict`, `PyList`, `PyTuple` & `PySet`
\ No newline at end of file
diff --git a/src/types/dict.rs b/src/types/dict.rs
index 0d2e6ff335f..1d6b477736c 100644
--- a/src/types/dict.rs
+++ b/src/types/dict.rs
@@ -534,6 +534,14 @@ impl<'py> Iterator for BoundDictIterator<'py> {
         (len, Some(len))
     }
 
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
+
     #[inline]
     #[cfg(Py_GIL_DISABLED)]
     fn fold<B, F>(mut self, init: B, mut f: F) -> B
@@ -736,6 +744,14 @@ mod borrowed_iter {
             let len = self.len();
             (len, Some(len))
         }
+
+        #[inline]
+        fn count(self) -> usize
+        where
+            Self: Sized,
+        {
+            self.len()
+        }
     }
 
     impl ExactSizeIterator for BorrowedDictIter<'_, '_> {
diff --git a/src/types/frozenset.rs b/src/types/frozenset.rs
index 954c49b5902..ee9a9b11f1f 100644
--- a/src/types/frozenset.rs
+++ b/src/types/frozenset.rs
@@ -237,6 +237,14 @@ impl<'py> Iterator for BoundFrozenSetIterator<'py> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.remaining, Some(self.remaining))
     }
+
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
 }
 
 impl ExactSizeIterator for BoundFrozenSetIterator<'_> {
diff --git a/src/types/list.rs b/src/types/list.rs
index 45a69b93195..20023e0e146 100644
--- a/src/types/list.rs
+++ b/src/types/list.rs
@@ -631,6 +631,14 @@ impl<'py> Iterator for BoundListIterator<'py> {
         (len, Some(len))
     }
 
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
+
     #[inline]
     fn last(mut self) -> Option<Self::Item>
     where
diff --git a/src/types/set.rs b/src/types/set.rs
index d5e39ebc83d..aefe45fbd91 100644
--- a/src/types/set.rs
+++ b/src/types/set.rs
@@ -270,6 +270,14 @@ impl<'py> Iterator for BoundSetIterator<'py> {
     fn size_hint(&self) -> (usize, Option<usize>) {
         (self.remaining, Some(self.remaining))
     }
+
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
 }
 
 impl ExactSizeIterator for BoundSetIterator<'_> {
diff --git a/src/types/tuple.rs b/src/types/tuple.rs
index 9880c510aa0..1a61a3e39f8 100644
--- a/src/types/tuple.rs
+++ b/src/types/tuple.rs
@@ -376,6 +376,14 @@ impl<'py> Iterator for BoundTupleIterator<'py> {
         (len, Some(len))
     }
 
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
+
     #[inline]
     fn last(mut self) -> Option<Self::Item>
     where
@@ -476,6 +484,14 @@ impl<'a, 'py> Iterator for BorrowedTupleIterator<'a, 'py> {
         (len, Some(len))
     }
 
+    #[inline]
+    fn count(self) -> usize
+    where
+        Self: Sized,
+    {
+        self.len()
+    }
+
     #[inline]
     fn last(mut self) -> Option<Self::Item>
     where