From b2f2774d329ff3c1dfadf3e497e1e2a5f447fd06 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Sun, 19 Nov 2023 00:54:25 +0100
Subject: [PATCH 01/11] DEP: Deprecate ravel

---
 doc/source/whatsnew/v2.2.0.rst  | 1 +
 pandas/core/series.py           | 5 +++++
 pandas/tests/series/test_api.py | 4 +++-
 3 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst
index a33322aebab34..a2c6db1f69066 100644
--- a/doc/source/whatsnew/v2.2.0.rst
+++ b/doc/source/whatsnew/v2.2.0.rst
@@ -266,6 +266,7 @@ Other Deprecations
 - Deprecated :func:`read_gbq` and :meth:`DataFrame.to_gbq`. Use ``pandas_gbq.read_gbq`` and ``pandas_gbq.to_gbq`` instead https://pandas-gbq.readthedocs.io/en/latest/api.html (:issue:`55525`)
 - Deprecated :meth:`.DataFrameGroupBy.fillna` and :meth:`.SeriesGroupBy.fillna`; use :meth:`.DataFrameGroupBy.ffill`, :meth:`.DataFrameGroupBy.bfill` for forward and backward filling or :meth:`.DataFrame.fillna` to fill with a single value (or the Series equivalents) (:issue:`55718`)
 - Deprecated :meth:`Index.format`, use ``index.astype(str)`` or ``index.map(formatter)`` instead (:issue:`55413`)
+- Deprecated :meth:`Series.ravel`, use ``np.ravel`` instead (:issue:`52511`)
 - Deprecated ``year``, ``month``, ``quarter``, ``day``, ``hour``, ``minute``, and ``second`` keywords in the :class:`PeriodIndex` constructor, use :meth:`PeriodIndex.from_fields` instead (:issue:`55960`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_clipboard`. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_csv` except ``path_or_buf``. (:issue:`54229`)
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 1bbd10429ea22..bf469d91a59c4 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -861,6 +861,11 @@ def ravel(self, order: str = "C") -> ArrayLike:
         >>> s.ravel()
         array([1, 2, 3])
         """
+        warnings.warn(
+            "Series.ravel is deprecated. Use numpy.ravel directly.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         arr = self._values.ravel(order=order)
         if isinstance(arr, np.ndarray) and using_copy_on_write():
             arr.flags.writeable = False
diff --git a/pandas/tests/series/test_api.py b/pandas/tests/series/test_api.py
index a39b3ff7e6f2b..97739e589d157 100644
--- a/pandas/tests/series/test_api.py
+++ b/pandas/tests/series/test_api.py
@@ -140,7 +140,9 @@ def test_ndarray_compat_like_func(self):
     def test_ndarray_compat_ravel(self):
         # ravel
         s = Series(np.random.default_rng(2).standard_normal(10))
-        tm.assert_almost_equal(s.ravel(order="F"), s.values.ravel(order="F"))
+        with tm.assert_produces_warning(FutureWarning, match="ravel is deprecated"):
+            result = s.ravel(order="F")
+        tm.assert_almost_equal(result, s.values.ravel(order="F"))
 
     def test_empty_method(self):
         s_empty = Series(dtype=object)

From dd9cfe636a90007c120c5b630b53850482ea893b Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Sun, 19 Nov 2023 15:00:51 +0100
Subject: [PATCH 02/11] Fix ravel deprecations

---
 pandas/_testing/asserters.py         | 2 ++
 pandas/core/reshape/pivot.py         | 2 +-
 pandas/tests/copy_view/test_array.py | 3 ++-
 3 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/pandas/_testing/asserters.py b/pandas/_testing/asserters.py
index 0d8fb7bfce33a..55cf734c32eae 100644
--- a/pandas/_testing/asserters.py
+++ b/pandas/_testing/asserters.py
@@ -426,6 +426,8 @@ def assert_is_valid_plot_return_object(objs) -> None:
     from matplotlib.axes import Axes
 
     if isinstance(objs, (Series, np.ndarray)):
+        if isinstance(objs, Series):
+            objs = objs._values
         for el in objs.ravel():
             msg = (
                 "one of 'objs' is not a matplotlib Axes instance, "
diff --git a/pandas/core/reshape/pivot.py b/pandas/core/reshape/pivot.py
index 79354fdd12a2d..94fcb3c2831f7 100644
--- a/pandas/core/reshape/pivot.py
+++ b/pandas/core/reshape/pivot.py
@@ -316,7 +316,7 @@ def _add_margins(
 
         cols = result.select_dtypes([dtype]).columns
         margin_dummy[cols] = margin_dummy[cols].apply(
-            maybe_downcast_to_dtype, args=(dtype,)
+            lambda x: maybe_downcast_to_dtype(x._values, dtype)
         )
     result = result._append(margin_dummy)
     result.index.names = row_names
diff --git a/pandas/tests/copy_view/test_array.py b/pandas/tests/copy_view/test_array.py
index 62a6a3374e612..e5d0aafb80b35 100644
--- a/pandas/tests/copy_view/test_array.py
+++ b/pandas/tests/copy_view/test_array.py
@@ -116,7 +116,8 @@ def test_series_to_numpy(using_copy_on_write):
 @pytest.mark.parametrize("order", ["F", "C"])
 def test_ravel_read_only(using_copy_on_write, order):
     ser = Series([1, 2, 3])
-    arr = ser.ravel(order=order)
+    with tm.assert_produces_warning(FutureWarning, match="is deprecated"):
+        arr = ser.ravel(order=order)
     if using_copy_on_write:
         assert arr.flags.writeable is False
     assert np.shares_memory(get_array(ser), arr)

From 054ca87d24b1766d33dd448451601a9febd57cf1 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Sun, 19 Nov 2023 17:51:41 +0100
Subject: [PATCH 03/11] Update pivot.py

---
 pandas/core/reshape/pivot.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pandas/core/reshape/pivot.py b/pandas/core/reshape/pivot.py
index 94fcb3c2831f7..a3a6febbd4b40 100644
--- a/pandas/core/reshape/pivot.py
+++ b/pandas/core/reshape/pivot.py
@@ -309,6 +309,10 @@ def _add_margins(
 
     row_names = result.index.names
     # check the result column and leave floats
+
+    def cast_types(x, dtype):
+        return maybe_downcast_to_dtype(x._values, dtype)
+
     for dtype in set(result.dtypes):
         if isinstance(dtype, ExtensionDtype):
             # Can hold NA already
@@ -316,7 +320,7 @@ def _add_margins(
 
         cols = result.select_dtypes([dtype]).columns
         margin_dummy[cols] = margin_dummy[cols].apply(
-            lambda x: maybe_downcast_to_dtype(x._values, dtype)
+            cast_types, arg=(dtype, )
         )
     result = result._append(margin_dummy)
     result.index.names = row_names

From 5a153892425a7dec5acb925d86ceb741c1bf0338 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Sun, 19 Nov 2023 17:54:36 +0100
Subject: [PATCH 04/11] Fix doctest

---
 pandas/core/series.py | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index bf469d91a59c4..522e2e5eb09b6 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -858,14 +858,9 @@ def ravel(self, order: str = "C") -> ArrayLike:
         Examples
         --------
         >>> s = pd.Series([1, 2, 3])
-        >>> s.ravel()
+        >>> s.ravel()  # doctest: +SKIP
         array([1, 2, 3])
         """
-        warnings.warn(
-            "Series.ravel is deprecated. Use numpy.ravel directly.",
-            FutureWarning,
-            stacklevel=find_stack_level(),
-        )
         arr = self._values.ravel(order=order)
         if isinstance(arr, np.ndarray) and using_copy_on_write():
             arr.flags.writeable = False
@@ -943,6 +938,11 @@ def view(self, dtype: Dtype | None = None) -> Series:
         4      2
         dtype: int8
         """
+        warnings.warn(
+            "Series.view is deprecated and will be removed in a future version.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         # self.array instead of self._values so we piggyback on NumpyExtensionArray
         #  implementation
         res_values = self.array.view(dtype)

From 28fb76c43074492123e058302d84e8c76d2550fc Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Mon, 20 Nov 2023 00:10:51 +0100
Subject: [PATCH 05/11] Fix view

---
 pandas/core/series.py | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index 522e2e5eb09b6..699ab37e90c2c 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -861,6 +861,11 @@ def ravel(self, order: str = "C") -> ArrayLike:
         >>> s.ravel()  # doctest: +SKIP
         array([1, 2, 3])
         """
+        warnings.warn(
+            "Series.ravel is deprecated. Use numpy.ravel directly.",
+            FutureWarning,
+            stacklevel=find_stack_level(),
+        )
         arr = self._values.ravel(order=order)
         if isinstance(arr, np.ndarray) and using_copy_on_write():
             arr.flags.writeable = False
@@ -938,11 +943,6 @@ def view(self, dtype: Dtype | None = None) -> Series:
         4      2
         dtype: int8
         """
-        warnings.warn(
-            "Series.view is deprecated and will be removed in a future version.",
-            FutureWarning,
-            stacklevel=find_stack_level(),
-        )
         # self.array instead of self._values so we piggyback on NumpyExtensionArray
         #  implementation
         res_values = self.array.view(dtype)

From 636e3c44c71c22316ca4dc208b320943e0b6b121 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Mon, 20 Nov 2023 01:49:55 +0100
Subject: [PATCH 06/11] Fix

---
 pandas/core/reshape/pivot.py | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/pandas/core/reshape/pivot.py b/pandas/core/reshape/pivot.py
index a3a6febbd4b40..bb387079403d2 100644
--- a/pandas/core/reshape/pivot.py
+++ b/pandas/core/reshape/pivot.py
@@ -310,7 +310,7 @@ def _add_margins(
     row_names = result.index.names
     # check the result column and leave floats
 
-    def cast_types(x, dtype):
+    def _cast_types(x, dtype):
         return maybe_downcast_to_dtype(x._values, dtype)
 
     for dtype in set(result.dtypes):
@@ -319,9 +319,7 @@ def cast_types(x, dtype):
             continue
 
         cols = result.select_dtypes([dtype]).columns
-        margin_dummy[cols] = margin_dummy[cols].apply(
-            cast_types, arg=(dtype, )
-        )
+        margin_dummy[cols] = margin_dummy[cols].apply(_cast_types, args=(dtype,))
     result = result._append(margin_dummy)
     result.index.names = row_names
 

From d48e5ca16998d2c9dbda400c65710da9903d550b Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Tue, 21 Nov 2023 20:53:48 +0100
Subject: [PATCH 07/11] Update

---
 pandas/core/dtypes/cast.py   | 2 ++
 pandas/core/reshape/pivot.py | 7 +++----
 pandas/core/series.py        | 7 +++++--
 3 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/pandas/core/dtypes/cast.py b/pandas/core/dtypes/cast.py
index 0ad652bd5aa64..79747513eabe9 100644
--- a/pandas/core/dtypes/cast.py
+++ b/pandas/core/dtypes/cast.py
@@ -261,6 +261,8 @@ def maybe_downcast_to_dtype(result: ArrayLike, dtype: str | np.dtype) -> ArrayLi
     try to cast to the specified dtype (e.g. convert back to bool/int
     or could be an astype of float64->float32
     """
+    if isinstance(result, ABCSeries):
+        result = result._values
     do_round = False
 
     if isinstance(dtype, str):
diff --git a/pandas/core/reshape/pivot.py b/pandas/core/reshape/pivot.py
index bb387079403d2..974578445f503 100644
--- a/pandas/core/reshape/pivot.py
+++ b/pandas/core/reshape/pivot.py
@@ -310,16 +310,15 @@ def _add_margins(
     row_names = result.index.names
     # check the result column and leave floats
 
-    def _cast_types(x, dtype):
-        return maybe_downcast_to_dtype(x._values, dtype)
-
     for dtype in set(result.dtypes):
         if isinstance(dtype, ExtensionDtype):
             # Can hold NA already
             continue
 
         cols = result.select_dtypes([dtype]).columns
-        margin_dummy[cols] = margin_dummy[cols].apply(_cast_types, args=(dtype,))
+        margin_dummy[cols] = margin_dummy[cols].apply(
+            maybe_downcast_to_dtype, args=(dtype,)
+        )
     result = result._append(margin_dummy)
     result.index.names = row_names
 
diff --git a/pandas/core/series.py b/pandas/core/series.py
index 699ab37e90c2c..1d0146bc4e875 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -846,6 +846,8 @@ def ravel(self, order: str = "C") -> ArrayLike:
         """
         Return the flattened underlying data as an ndarray or ExtensionArray.
 
+        .. deprecated:: 2.2.0
+
         Returns
         -------
         numpy.ndarray or ExtensionArray
@@ -862,9 +864,10 @@ def ravel(self, order: str = "C") -> ArrayLike:
         array([1, 2, 3])
         """
         warnings.warn(
-            "Series.ravel is deprecated. Use numpy.ravel directly.",
+            "Series.ravel is deprecated. The underlying array is already 1D, so "
+            "ravel is not necessary.",
             FutureWarning,
-            stacklevel=find_stack_level(),
+            stacklevel=2,
         )
         arr = self._values.ravel(order=order)
         if isinstance(arr, np.ndarray) and using_copy_on_write():

From 146e1aacbda8c59472d95560a605c2a775bd913b Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Tue, 21 Nov 2023 20:54:21 +0100
Subject: [PATCH 08/11] Update whatsnew

---
 doc/source/whatsnew/v2.2.0.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/doc/source/whatsnew/v2.2.0.rst b/doc/source/whatsnew/v2.2.0.rst
index 7cefbda6cb345..8437d97c69f48 100644
--- a/doc/source/whatsnew/v2.2.0.rst
+++ b/doc/source/whatsnew/v2.2.0.rst
@@ -266,7 +266,7 @@ Other Deprecations
 - Deprecated :func:`read_gbq` and :meth:`DataFrame.to_gbq`. Use ``pandas_gbq.read_gbq`` and ``pandas_gbq.to_gbq`` instead https://pandas-gbq.readthedocs.io/en/latest/api.html (:issue:`55525`)
 - Deprecated :meth:`.DataFrameGroupBy.fillna` and :meth:`.SeriesGroupBy.fillna`; use :meth:`.DataFrameGroupBy.ffill`, :meth:`.DataFrameGroupBy.bfill` for forward and backward filling or :meth:`.DataFrame.fillna` to fill with a single value (or the Series equivalents) (:issue:`55718`)
 - Deprecated :meth:`Index.format`, use ``index.astype(str)`` or ``index.map(formatter)`` instead (:issue:`55413`)
-- Deprecated :meth:`Series.ravel`, use ``np.ravel`` instead (:issue:`52511`)
+- Deprecated :meth:`Series.ravel`, the underlying array is already 1D, so ravel is not necessary (:issue:`52511`)
 - Deprecated ``year``, ``month``, ``quarter``, ``day``, ``hour``, ``minute``, and ``second`` keywords in the :class:`PeriodIndex` constructor, use :meth:`PeriodIndex.from_fields` instead (:issue:`55960`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_clipboard`. (:issue:`54229`)
 - Deprecated allowing non-keyword arguments in :meth:`DataFrame.to_csv` except ``path_or_buf``. (:issue:`54229`)

From 571bc1a158c72b590114588d5f35b6bed1e24577 Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Tue, 21 Nov 2023 21:23:46 +0100
Subject: [PATCH 09/11] FIx

---
 pandas/tests/dtypes/cast/test_downcast.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/pandas/tests/dtypes/cast/test_downcast.py b/pandas/tests/dtypes/cast/test_downcast.py
index c01eac746455c..9430ba2c478ae 100644
--- a/pandas/tests/dtypes/cast/test_downcast.py
+++ b/pandas/tests/dtypes/cast/test_downcast.py
@@ -56,8 +56,8 @@ def test_downcast_booleans():
     ser = Series([True, True, False])
     result = maybe_downcast_to_dtype(ser, np.dtype(np.float64))
 
-    expected = ser
-    tm.assert_series_equal(result, expected)
+    expected = ser.values
+    tm.assert_numpy_array_equal(result, expected)
 
 
 def test_downcast_conversion_no_nan(any_real_numpy_dtype):

From d54a80c3a514122dfde5cce82ec96aa69c940a4e Mon Sep 17 00:00:00 2001
From: Patrick Hoefler <61934744+phofl@users.noreply.github.com>
Date: Tue, 21 Nov 2023 23:03:15 +0100
Subject: [PATCH 10/11] Add note

---
 pandas/core/series.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index 1d0146bc4e875..398cf349d63a4 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -847,6 +847,9 @@ def ravel(self, order: str = "C") -> ArrayLike:
         Return the flattened underlying data as an ndarray or ExtensionArray.
 
         .. deprecated:: 2.2.0
+            Series.ravel is deprecated. The underlying array is already 1D, so
+            ravel is not necessary.  Use `to_numpy()` for conversion to a numpy
+            array instead.
 
         Returns
         -------
@@ -865,7 +868,8 @@ def ravel(self, order: str = "C") -> ArrayLike:
         """
         warnings.warn(
             "Series.ravel is deprecated. The underlying array is already 1D, so "
-            "ravel is not necessary.",
+            "ravel is not necessary.  Use `to_numpy()` for conversion to a numpy "
+            "array instead.",
             FutureWarning,
             stacklevel=2,
         )

From 4afe81c39787de5908eed6473af71768a3a5b88d Mon Sep 17 00:00:00 2001
From: Joris Van den Bossche <jorisvandenbossche@gmail.com>
Date: Mon, 27 Nov 2023 12:23:28 +0100
Subject: [PATCH 11/11] Update pandas/core/series.py

---
 pandas/core/series.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/pandas/core/series.py b/pandas/core/series.py
index 138f7d4319f7e..82842e84acb60 100644
--- a/pandas/core/series.py
+++ b/pandas/core/series.py
@@ -849,7 +849,7 @@ def ravel(self, order: str = "C") -> ArrayLike:
 
         .. deprecated:: 2.2.0
             Series.ravel is deprecated. The underlying array is already 1D, so
-            ravel is not necessary.  Use `to_numpy()` for conversion to a numpy
+            ravel is not necessary.  Use :meth:`to_numpy` for conversion to a numpy
             array instead.
 
         Returns