From 0b56b31ed873d11557a0c36eda7b60b9549b0c94 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Lo=C3=AFc=20Diridollou?= <loic.diridollou@gmail.com>
Date: Sat, 7 Jun 2025 09:29:15 -0400
Subject: [PATCH] GH1241 Add cumsum method on TimedeltaSeries

---
 pandas-stubs/core/series.pyi |  7 +++++++
 tests/test_series.py         | 11 +++++++++++
 2 files changed, 18 insertions(+)

diff --git a/pandas-stubs/core/series.pyi b/pandas-stubs/core/series.pyi
index 8ea4612b..327b0a2b 100644
--- a/pandas-stubs/core/series.pyi
+++ b/pandas-stubs/core/series.pyi
@@ -2334,6 +2334,13 @@ class TimedeltaSeries(Series[Timedelta]):
         **kwargs: Any,
     ) -> Timedelta: ...
     def diff(self, periods: int = ...) -> TimedeltaSeries: ...  # type: ignore[override] # pyright: ignore[reportIncompatibleMethodOverride]
+    def cumsum(
+        self,
+        axis: AxisIndex | None = ...,
+        skipna: _bool = ...,
+        *args: Any,
+        **kwargs: Any,
+    ) -> TimedeltaSeries: ...
 
 class PeriodSeries(Series[Period]):
     @property
diff --git a/tests/test_series.py b/tests/test_series.py
index 57051997..99e6d670 100644
--- a/tests/test_series.py
+++ b/tests/test_series.py
@@ -3813,3 +3813,14 @@ def test_series_items() -> None:
     s = pd.Series(data=[1, 2, 3, 4], index=["cow", "coal", "coalesce", ""])
     check(assert_type(next(s.items()), tuple[Hashable, int]), tuple)
     check(assert_type(s.items(), Iterator[tuple[Hashable, int]]), Iterator)
+
+
+def test_cumsum_timedelta() -> None:
+
+    s = pd.Series(pd.to_timedelta([1, 2, 3], "h"))
+    check(assert_type(s.cumsum(), "TimedeltaSeries"), pd.Series, pd.Timedelta)
+    check(
+        assert_type(pd.Timestamp(0) + s.cumsum(), "TimestampSeries"),
+        pd.Series,
+        pd.Timestamp,
+    )