BUG: Regression in astype not casting to bytes (#39484)

Author: phofl

doc/source/whatsnew/v1.2.2.rst

@@ -17,6 +17,7 @@ Fixed regressions
 
 - Fixed regression in :func:`read_excel` that caused it to raise ``AttributeError`` when checking version of older xlrd versions (:issue:`38955`)
 - Fixed regression in :class:`DataFrame` constructor reordering element when construction from datetime ndarray with dtype not ``"datetime64[ns]"`` (:issue:`39422`)
+- Fixed regression in :class:`DataFrame.astype` and :class:`Series.astype` not casting to bytes dtype (:issue:`39474`)
 - Fixed regression in :meth:`~DataFrame.to_pickle` failing to create bz2/xz compressed pickle files with ``protocol=5`` (:issue:`39002`)
 - Fixed regression in :func:`pandas.testing.assert_series_equal` and :func:`pandas.testing.assert_frame_equal` always raising ``AssertionError`` when comparing extension dtypes (:issue:`39410`)
 - Fixed regression in :meth:`~DataFrame.to_csv` opening ``codecs.StreamWriter`` in binary mode instead of in text mode and ignoring user-provided ``mode`` (:issue:`39247`)

pandas/core/dtypes/cast.py

@@ -1221,7 +1221,7 @@ def soft_convert_objects(
             values = lib.maybe_convert_objects(
                 values, convert_datetime=datetime, convert_timedelta=timedelta
             )
-        except OutOfBoundsDatetime:
+        except (OutOfBoundsDatetime, ValueError):
             return values
 
     if numeric and is_object_dtype(values.dtype):

pandas/core/internals/blocks.py

@@ -2254,7 +2254,7 @@ class ObjectBlock(Block):
     _can_hold_na = True
 
     def _maybe_coerce_values(self, values):
-        if issubclass(values.dtype.type, (str, bytes)):
+        if issubclass(values.dtype.type, str):
             values = np.array(values, dtype=object)
         return values
 

pandas/tests/frame/methods/test_astype.py

@@ -651,3 +651,8 @@ def test_astype_dt64_to_string(self, frame_or_series, tz_naive_fixture, request)
         # For non-NA values, we should match what we get for non-EA str
         alt = obj.astype(str)
         assert np.all(alt.iloc[1:] == result.iloc[1:])
+
+    def test_astype_bytes(self):
+        # GH#39474
+        result = DataFrame(["foo", "bar", "baz"]).astype(bytes)
+        assert result.dtypes[0] == np.dtype("S3")

pandas/tests/series/methods/test_astype.py

@@ -341,6 +341,11 @@ def test_astype_unicode(self):
             reload(sys)
             sys.setdefaultencoding(former_encoding)
 
+    def test_astype_bytes(self):
+        # GH#39474
+        result = Series(["foo", "bar", "baz"]).astype(bytes)
+        assert result.dtypes == np.dtype("S3")
+
 
 class TestAstypeCategorical:
     def test_astype_categorical_invalid_conversions(self):