DEPR: DataFrame.resample axis parameter

doc/source/whatsnew/v2.1.0.rst

@@ -99,6 +99,7 @@ Deprecations
 - Deprecated ``axis=1`` in :meth:`DataFrame.groupby` and in :class:`Grouper` constructor, do ``frame.T.groupby(...)`` instead (:issue:`51203`)
 - Deprecated passing a :class:`DataFrame` to :meth:`DataFrame.from_records`, use :meth:`DataFrame.set_index` or :meth:`DataFrame.drop` instead (:issue:`51353`)
 - Deprecated accepting slices in :meth:`DataFrame.take`, call ``obj[slicer]`` or pass a sequence of integers instead (:issue:`51539`)
+- Deprecated ``axis=1`` in :meth:`DataFrame.resample`, do ``frame.T.resample(...)`` instead (:issue:`51778`)
 -
 
 .. ---------------------------------------------------------------------------

pandas/core/frame.py

@@ -11408,7 +11408,7 @@ def asfreq(
     def resample(
         self,
         rule,
-        axis: Axis = 0,
+        axis: Axis | lib.NoDefault = lib.no_default,
         closed: str | None = None,
         label: str | None = None,
         convention: str = "start",

pandas/core/generic.py

@@ -8531,7 +8531,7 @@ def between_time(
     def resample(
         self,
         rule,
-        axis: Axis = 0,
+        axis: Axis | lib.NoDefault = lib.no_default,
         closed: str | None = None,
         label: str | None = None,
         convention: str = "start",
@@ -8558,6 +8558,8 @@ def resample(
             Which axis to use for up- or down-sampling. For `Series` this parameter
             is unused and defaults to 0. Must be
             `DatetimeIndex`, `TimedeltaIndex` or `PeriodIndex`.
+            .. deprecated:: 2.0.0
+                Use frame.T.resample(...) instead.
         closed : {{'right', 'left'}}, default None
             Which side of bin interval is closed. The default is 'left'
             for all frequency offsets except for 'M', 'A', 'Q', 'BM',
@@ -8911,7 +8913,25 @@ def resample(
         """
         from pandas.core.resample import get_resampler
 
-        axis = self._get_axis_number(axis)
+        if axis is not lib.no_default:
+            axis = self._get_axis_number(axis)
+            if axis == 1:
+                warnings.warn(
+                    "DataFrame.resample with axis=1 is deprecated. Do "
+                    "`frame.T.resample(...)` without axis instead.",
+                    FutureWarning,
+                    stacklevel=find_stack_level(),
+                )
+            else:
+                warnings.warn(
+                    "The 'axis' keyword in DataFrame.resample is deprecated and "
+                    "will be removed in a future version.",
+                    FutureWarning,
+                    stacklevel=find_stack_level(),
+                )
+        else:
+            axis = 0
+
         return get_resampler(
             cast("Series | DataFrame", self),
             freq=rule,

pandas/core/series.py

@@ -5570,7 +5570,7 @@ def asfreq(
     def resample(
         self,
         rule,
-        axis: Axis = 0,
+        axis: Axis | lib.NoDefault = lib.no_default,
         closed: str | None = None,
         label: str | None = None,
         convention: str = "start",
@@ -5581,6 +5581,14 @@ def resample(
         offset: TimedeltaConvertibleTypes | None = None,
         group_keys: bool | lib.NoDefault = no_default,
     ) -> Resampler:
+        if axis is not lib.no_default:
+            warnings.warn(
+                "Series resample axis keyword is deprecated and will be removed in a "
+                "future version.",
+                FutureWarning,
+                stacklevel=find_stack_level(),
+            )
+
         return super().resample(
             rule=rule,
             axis=axis,

pandas/tests/resample/test_datetime_index.py

@@ -641,12 +641,16 @@ def test_resample_dup_index():
         columns=[Period(year=2000, month=i + 1, freq="M") for i in range(12)],
     )
     df.iloc[3, :] = np.nan
-    result = df.resample("Q", axis=1).mean()
-    msg = "DataFrame.groupby with axis=1 is deprecated"
-    with tm.assert_produces_warning(FutureWarning, match=msg):
-        expected = df.groupby(lambda x: int((x.month - 1) / 3), axis=1).mean()
-    expected.columns = [Period(year=2000, quarter=i + 1, freq="Q") for i in range(4)]
-    tm.assert_frame_equal(result, expected)
+    warning_msg = "DataFrame.resample with axis=1 is deprecated."
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        result = df.resample("Q", axis=1).mean()
+        msg = "DataFrame.groupby with axis=1 is deprecated"
+        with tm.assert_produces_warning(FutureWarning, match=msg):
+            expected = df.groupby(lambda x: int((x.month - 1) / 3), axis=1).mean()
+        expected.columns = [
+            Period(year=2000, quarter=i + 1, freq="Q") for i in range(4)
+        ]
+        tm.assert_frame_equal(result, expected)
 
 
 def test_resample_reresample(unit):
@@ -729,9 +733,11 @@ def test_resample_axis1(unit):
     rng = date_range("1/1/2000", "2/29/2000").as_unit(unit)
     df = DataFrame(np.random.randn(3, len(rng)), columns=rng, index=["a", "b", "c"])
 
-    result = df.resample("M", axis=1).mean()
-    expected = df.T.resample("M").mean().T
-    tm.assert_frame_equal(result, expected)
+    warning_msg = "DataFrame.resample with axis=1 is deprecated."
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        result = df.resample("M", axis=1).mean()
+        expected = df.T.resample("M").mean().T
+        tm.assert_frame_equal(result, expected)
 
 
 @pytest.mark.parametrize("freq", ["t", "5t", "15t", "30t", "4h", "12h"])

pandas/tests/resample/test_resample_api.py

@@ -570,9 +570,13 @@ def test_multi_agg_axis_1_raises(func):
     index = date_range(datetime(2005, 1, 1), datetime(2005, 1, 10), freq="D")
     index.name = "date"
     df = DataFrame(np.random.rand(10, 2), columns=list("AB"), index=index).T
-    res = df.resample("M", axis=1)
-    with pytest.raises(NotImplementedError, match="axis other than 0 is not supported"):
-        res.agg(func)
+    warning_msg = "DataFrame.resample with axis=1 is deprecated."
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        res = df.resample("M", axis=1)
+        with pytest.raises(
+            NotImplementedError, match="axis other than 0 is not supported"
+        ):
+            res.agg(func)
 
 
 def test_agg_nested_dicts():
@@ -973,3 +977,33 @@ def test_args_kwargs_depr(method, raises):
         with tm.assert_produces_warning(FutureWarning, match=warn_msg):
             with pytest.raises(TypeError, match=error_msg_type):
                 func(*args, 1, 2, 3)
+
+
+def test_df_axis_param_depr():
+    np.random.seed(1234)
+    index = date_range(datetime(2005, 1, 1), datetime(2005, 1, 10), freq="D")
+    index.name = "date"
+    df = DataFrame(np.random.rand(10, 2), columns=list("AB"), index=index).T
+
+    # Deprication error when axis=1 is explicitly passed
+    warning_msg = "DataFrame.resample with axis=1 is deprecated."
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        df.resample("M", axis=1)
+
+    # Deprication error when axis=0 is explicitly passed
+    df = df.T
+    warning_msg = (
+        "The 'axis' keyword in DataFrame.resample is deprecated and "
+        "will be removed in a future version."
+    )
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        df.resample("M", axis=0)
+
+
+def test_series_axis_param_depr():
+    warning_msg = (
+        "Series resample axis keyword is deprecated and will be removed in a "
+        "future version."
+    )
+    with tm.assert_produces_warning(FutureWarning, match=warning_msg):
+        test_series.resample("H", axis=0)