DEPR: Enforce DTI.to_series(keep_tz) removal (pandas-dev#48823)

Author: mroeschke

doc/source/whatsnew/v2.0.0.rst

@@ -144,6 +144,7 @@ Deprecations
 
 Removal of prior version deprecations/changes
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+- Removed ``keep_tz`` argument in :meth:`DatetimeIndex.to_series` (:issue:`29731`)
 - Remove arguments ``names`` and ``dtype`` from :meth:`Index.copy` and ``levels`` and ``codes`` from :meth:`MultiIndex.copy` (:issue:`35853`, :issue:`36685`)
 - Disallow passing non-round floats to :class:`Timestamp` with ``unit="M"`` or ``unit="Y"`` (:issue:`47266`)
 - Removed the ``numeric_only`` keyword from :meth:`Categorical.min` and :meth:`Categorical.max` in favor of ``skipna`` (:issue:`48821`)

pandas/core/indexes/datetimes.py

@@ -518,35 +518,14 @@ def _get_time_micros(self) -> npt.NDArray[np.int64]:
         micros[self._isnan] = -1
         return micros
 
-    def to_series(self, keep_tz=lib.no_default, index=None, name=None):
+    def to_series(self, index=None, name=None):
         """
         Create a Series with both index and values equal to the index keys.
 
         Useful with map for returning an indexer based on an index.
 
         Parameters
         ----------
-        keep_tz : optional, defaults True
-            Return the data keeping the timezone.
-
-            If keep_tz is True:
-
-              If the timezone is not set, the resulting
-              Series will have a datetime64[ns] dtype.
-
-              Otherwise the Series will have an datetime64[ns, tz] dtype; the
-              tz will be preserved.
-
-            If keep_tz is False:
-
-              Series will have a datetime64[ns] dtype. TZ aware
-              objects will have the tz removed.
-
-            .. versionchanged:: 1.0.0
-                The default value is now True.  In a future version,
-                this keyword will be removed entirely.  Stop passing the
-                argument to obtain the future behavior and silence the warning.
-
         index : Index, optional
             Index of resulting Series. If None, defaults to original index.
         name : str, optional
@@ -564,35 +543,7 @@ def to_series(self, keep_tz=lib.no_default, index=None, name=None):
         if name is None:
             name = self.name
 
-        if keep_tz is not lib.no_default:
-            if keep_tz:
-                warnings.warn(
-                    "The 'keep_tz' keyword in DatetimeIndex.to_series "
-                    "is deprecated and will be removed in a future version. "
-                    "You can stop passing 'keep_tz' to silence this warning.",
-                    FutureWarning,
-                    stacklevel=find_stack_level(),
-                )
-            else:
-                warnings.warn(
-                    "Specifying 'keep_tz=False' is deprecated and this "
-                    "option will be removed in a future release. If "
-                    "you want to remove the timezone information, you "
-                    "can do 'idx.tz_convert(None)' before calling "
-                    "'to_series'.",
-                    FutureWarning,
-                    stacklevel=find_stack_level(),
-                )
-        else:
-            keep_tz = True
-
-        if keep_tz and self.tz is not None:
-            # preserve the tz & copy
-            values = self.copy(deep=True)
-        else:
-            # error: Incompatible types in assignment (expression has type
-            # "Union[ExtensionArray, ndarray]", variable has type "DatetimeIndex")
-            values = self._values.view("M8[ns]").copy()  # type: ignore[assignment]
+        values = self._values.copy()
 
         return Series(values, index=index, name=name)
 

pandas/tests/frame/indexing/test_setitem.py

@@ -779,11 +779,7 @@ def test_setitem_dt64series(self, idx, expected):
         # convert to utc
         df = DataFrame(np.random.randn(2, 1), columns=["A"])
         df["B"] = idx
-
-        with tm.assert_produces_warning(FutureWarning) as m:
-            df["B"] = idx.to_series(keep_tz=False, index=[0, 1])
-        msg = "do 'idx.tz_convert(None)' before calling"
-        assert msg in str(m[0].message)
+        df["B"] = idx.to_series(index=[0, 1]).dt.tz_convert(None)
 
         result = df["B"]
         comp = Series(idx.tz_convert("UTC").tz_localize(None), name="B")

pandas/tests/indexes/datetimes/methods/test_to_series.py

@@ -1,5 +1,4 @@
 import numpy as np
-import pytest
 
 from pandas import (
     DatetimeIndex,
@@ -9,32 +8,11 @@
 
 
 class TestToSeries:
-    @pytest.fixture
-    def idx_expected(self):
+    def test_to_series(self):
         naive = DatetimeIndex(["2013-1-1 13:00", "2013-1-2 14:00"], name="B")
         idx = naive.tz_localize("US/Pacific")
 
         expected = Series(np.array(idx.tolist(), dtype="object"), name="B")
-
+        result = idx.to_series(index=[0, 1])
         assert expected.dtype == idx.dtype
-        return idx, expected
-
-    def test_to_series_keep_tz_deprecated_true(self, idx_expected):
-        # convert to series while keeping the timezone
-        idx, expected = idx_expected
-
-        msg = "stop passing 'keep_tz'"
-        with tm.assert_produces_warning(FutureWarning) as m:
-            result = idx.to_series(keep_tz=True, index=[0, 1])
-        assert msg in str(m[0].message)
-
         tm.assert_series_equal(result, expected)
-
-    def test_to_series_keep_tz_deprecated_false(self, idx_expected):
-        idx, expected = idx_expected
-
-        with tm.assert_produces_warning(FutureWarning) as m:
-            result = idx.to_series(keep_tz=False, index=[0, 1])
-        tm.assert_series_equal(result, expected.dt.tz_convert(None))
-        msg = "do 'idx.tz_convert(None)' before calling"
-        assert msg in str(m[0].message)