Backport PR #47051 on branch 1.4.x (BUG: DataFrame.shift shows different behavior for axis=1 when freq is specified) (#47158)

Backport PR #47051: BUG: `DataFrame.shift` shows different behavior for `axis=1` when `freq` is specified

Co-authored-by: Wenjun Si <[email protected]>

Author: meeseeksmachine

doc/source/whatsnew/v1.4.3.rst

@@ -22,6 +22,7 @@ Fixed regressions
 - Fixed regression in :func:`read_csv` with ``index_col=False`` identifying first row as index names when ``header=None`` (:issue:`46955`)
 - Fixed regression in :meth:`.DataFrameGroupBy.agg` when used with list-likes or dict-likes and ``axis=1`` that would give incorrect results; now raises ``NotImplementedError`` (:issue:`46995`)
 - Fixed regression in :meth:`DataFrame.resample` and :meth:`DataFrame.rolling` when used with list-likes or dict-likes and ``axis=1`` that would raise an unintuitive error message; now raises ``NotImplementedError`` (:issue:`46904`)
+- Fixed regression in :meth:`DataFrame.shift` when ``axis`` is ``columns`` and ``fill_value`` is absent, ``freq`` is ignored (:issue:`47039`)
 
 .. ---------------------------------------------------------------------------
 

pandas/core/frame.py

@@ -5333,7 +5333,13 @@ def shift(
         axis = self._get_axis_number(axis)
 
         ncols = len(self.columns)
-        if axis == 1 and periods != 0 and fill_value is lib.no_default and ncols > 0:
+        if (
+            axis == 1
+            and periods != 0
+            and freq is None
+            and fill_value is lib.no_default
+            and ncols > 0
+        ):
             # We will infer fill_value to match the closest column
 
             # Use a column that we know is valid for our column's dtype GH#38434

pandas/tests/frame/methods/test_shift.py

@@ -255,6 +255,16 @@ def test_shift_named_axis(self):
         result = df.shift(1, axis="columns")
         tm.assert_frame_equal(result, expected)
 
+    def test_shift_other_axis_with_freq(self, datetime_frame):
+        obj = datetime_frame.T
+        offset = offsets.BDay()
+
+        # GH#47039
+        shifted = obj.shift(5, freq=offset, axis=1)
+        assert len(shifted) == len(obj)
+        unshifted = shifted.shift(-5, freq=offset, axis=1)
+        tm.assert_equal(unshifted, obj)
+
     def test_shift_bool(self):
         df = DataFrame({"high": [True, False], "low": [False, False]})
         rs = df.shift(1)