BUG: DataFrame.shift shows different behavior for axis=1 when freq is specified

Author: wjsi

doc/source/whatsnew/v1.5.0.rst

@@ -780,6 +780,7 @@ Indexing
 - Bug in setting large integer values into :class:`Series` with ``float32`` or ``float16`` dtype incorrectly altering these values instead of coercing to ``float64`` dtype (:issue:`45844`)
 - Bug in :meth:`Series.asof` and :meth:`DataFrame.asof` incorrectly casting bool-dtype results to ``float64`` dtype (:issue:`16063`)
 - Bug in :meth:`NDFrame.xs`, :meth:`DataFrame.iterrows`, :meth:`DataFrame.loc` and :meth:`DataFrame.iloc` not always propagating metadata (:issue:`28283`)
+- Bug in :meth:`DataFrame.shift` when ``axis`` is ``columns`` and ``fill_value`` is absent, ``freq`` is ignored (:issue:`47039`)
 -
 
 Missing

pandas/core/frame.py

@@ -5507,7 +5507,13 @@ 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

@@ -259,6 +259,16 @@ 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)