BUG: copy.copy returning deep instead of shallow copy

Author: mroeschke

doc/source/whatsnew/v3.0.0.rst

@@ -1265,6 +1265,7 @@ Other
 - Bug in :meth:`Series.replace` and :meth:`DataFrame.replace` throwing ``ValueError`` when ``regex=True`` and all NA values. (:issue:`60688`)
 - Bug in :meth:`Series.to_string` when series contains complex floats with exponents (:issue:`60405`)
 - Bug in :meth:`read_csv` where chained fsspec TAR file and ``compression="infer"`` fails with ``tarfile.ReadError`` (:issue:`60028`)
+- Bug when calling :py:func:`copy.copy` on a :class:`DataFrame` or :class:`Series` which would return a deep copy instead of a shallow copy (:issue:`?`)
 - Bug in Dataframe Interchange Protocol implementation was returning incorrect results for data buffers' associated dtype, for string and datetime columns (:issue:`54781`)
 - Bug in ``Series.list`` methods not preserving the original :class:`Index`. (:issue:`58425`)
 - Bug in ``Series.list`` methods not preserving the original name. (:issue:`60522`)

pandas/core/generic.py

@@ -6680,8 +6680,8 @@ def copy(self, deep: bool = True) -> Self:
         )
 
     @final
-    def __copy__(self, deep: bool = True) -> Self:
-        return self.copy(deep=deep)
+    def __copy__(self) -> Self:
+        return self.copy(deep=False)
 
     @final
     def __deepcopy__(self, memo=None) -> Self:

pandas/core/indexes/base.py

@@ -1413,8 +1413,8 @@ def copy(
         return new_index
 
     @final
-    def __copy__(self, **kwargs) -> Self:
-        return self.copy(**kwargs)
+    def __copy__(self) -> Self:
+        return self.copy(deep=False)
 
     @final
     def __deepcopy__(self, memo=None) -> Self:

pandas/tests/generic/test_generic.py

@@ -307,6 +307,11 @@ def test_copy_and_deepcopy(self, frame_or_series, shape, func):
         assert obj_copy is not obj
         tm.assert_equal(obj_copy, obj)
 
+    def test_stdlib_copy_shallow_copies(self, frame_or_series):
+        obj = frame_or_series(range(3))
+        obj_copy = copy(obj)
+        assert tm.shares_memory(obj, obj_copy)
+
 
 class TestNDFrame:
     # tests that don't fit elsewhere