BUG: DataFrame.explode fails with str dtype

doc/source/whatsnew/index.rst

@@ -24,6 +24,7 @@ Version 2.3
 .. toctree::
    :maxdepth: 2
 
+   v2.3.1
    v2.3.0
 
 Version 2.2

doc/source/whatsnew/v2.3.1.rst

@@ -0,0 +1,44 @@
+.. _whatsnew_231:
+
+What's new in 2.3.1 (Month XX, 2025)
+---------------------------------------
+
+These are the changes in pandas 2.3.1. See :ref:`release` for a full changelog
+including other versions of pandas.
+
+{{ header }}
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_231.enhancements:
+
+Enhancements
+~~~~~~~~~~~~
+-
+
+.. _whatsnew_231.regressions:
+
+Fixed regressions
+~~~~~~~~~~~~~~~~~
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_231.bug_fixes:
+
+Bug fixes
+~~~~~~~~~
+- Fixed bug in :meth:`DataFrame.explode` and :meth:`Series.explode` where methods would fail with ``dtype="str"`` (:issue:`61623`)
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_231.other:
+
+Other
+~~~~~
+-
+
+.. ---------------------------------------------------------------------------
+.. _whatsnew_231.contributors:
+
+Contributors
+~~~~~~~~~~~~
+
+.. contributors:: v2.3.0..v2.3.1

pandas/core/arrays/arrow/array.py

@@ -1935,9 +1935,9 @@ def _explode(self):
         """
         # child class explode method supports only list types; return
         # default implementation for non list types.
-        if not (
-            pa.types.is_list(self.dtype.pyarrow_dtype)
-            or pa.types.is_large_list(self.dtype.pyarrow_dtype)
+        if not hasattr(self.dtype, "pyarrow_dtype") or (
+            not pa.types.is_list(self.dtype.pyarrow_dtype)
+            and not pa.types.is_large_list(self.dtype.pyarrow_dtype)
         ):
             return super()._explode()
         values = self

pandas/tests/frame/methods/test_explode.py

@@ -297,3 +297,11 @@ def test_multi_columns_nan_empty():
         index=[0, 0, 1, 2, 3, 3],
     )
     tm.assert_frame_equal(result, expected)
+
+
+def test_str_dtype():
+    # https://github.com/pandas-dev/pandas/pull/61623
+    df = pd.DataFrame({"a": ["x", "y"]}, dtype="str")
+    result = df.explode(column="a")
+    assert result is not df
+    tm.assert_frame_equal(result, df)

pandas/tests/series/methods/test_explode.py

@@ -175,3 +175,11 @@ def test_explode_pyarrow_non_list_type(ignore_index):
     result = ser.explode(ignore_index=ignore_index)
     expected = pd.Series([1, 2, 3], dtype="int64[pyarrow]", index=[0, 1, 2])
     tm.assert_series_equal(result, expected)
+
+
+def test_str_dtype():
+    # https://github.com/pandas-dev/pandas/pull/61623
+    ser = pd.Series(["x", "y"], dtype="str")
+    result = ser.explode()
+    assert result is not ser
+    tm.assert_series_equal(result, ser)