ENH: copy kwd for add_suffix/add_prefix (#47934)

* ENH: copy kwd for add_suffix/add_prefix

* GH ref

* test series

Author: jbrockmendel

doc/source/whatsnew/v1.5.0.rst

@@ -292,6 +292,7 @@ Other enhancements
 - :class:`Series` reducers (e.g. ``min``, ``max``, ``sum``, ``mean``) will now successfully operate when the dtype is numeric and ``numeric_only=True`` is provided; previously this would raise a ``NotImplementedError`` (:issue:`47500`)
 - :meth:`RangeIndex.union` now can return a :class:`RangeIndex` instead of a :class:`Int64Index` if the resulting values are equally spaced (:issue:`47557`, :issue:`43885`)
 - :meth:`DataFrame.compare` now accepts an argument ``result_names`` to allow the user to specify the result's names of both left and right DataFrame which are being compared. This is by default ``'self'`` and ``'other'`` (:issue:`44354`)
+- :meth:`Series.add_suffix`, :meth:`DataFrame.add_suffix`, :meth:`Series.add_prefix` and :meth:`DataFrame.add_prefix` support a ``copy`` argument. If ``False``, the underlying data is not copied in the returned object (:issue:`47934`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_150.notable_bug_fixes:

pandas/core/generic.py

@@ -4549,7 +4549,7 @@ def _update_inplace(self, result, verify_is_copy: bool_t = True) -> None:
         self._maybe_update_cacher(verify_is_copy=verify_is_copy, inplace=True)
 
     @final
-    def add_prefix(self: NDFrameT, prefix: str) -> NDFrameT:
+    def add_prefix(self: NDFrameT, prefix: str, copy: bool_t = True) -> NDFrameT:
         """
         Prefix labels with string `prefix`.
 
@@ -4560,6 +4560,10 @@ def add_prefix(self: NDFrameT, prefix: str) -> NDFrameT:
         ----------
         prefix : str
             The string to add before each label.
+        copy : bool, default True
+            Whether to copy the underlying data.
+
+             .. versionadded:: 1.5.0
 
         Returns
         -------
@@ -4610,10 +4614,10 @@ def add_prefix(self: NDFrameT, prefix: str) -> NDFrameT:
         # expected "NDFrameT")
         # error: Argument 1 to "rename" of "NDFrame" has incompatible type
         # "**Dict[str, partial[str]]"; expected "Union[str, int, None]"
-        return self._rename(**mapper)  # type: ignore[return-value, arg-type]
+        return self._rename(**mapper, copy=copy)  # type: ignore[return-value, arg-type]
 
     @final
-    def add_suffix(self: NDFrameT, suffix: str) -> NDFrameT:
+    def add_suffix(self: NDFrameT, suffix: str, copy: bool_t = True) -> NDFrameT:
         """
         Suffix labels with string `suffix`.
 
@@ -4624,6 +4628,10 @@ def add_suffix(self: NDFrameT, suffix: str) -> NDFrameT:
         ----------
         suffix : str
             The string to add after each label.
+        copy : bool, default True
+            Whether to copy the underlying data.
+
+             .. versionadded:: 1.5.0
 
         Returns
         -------
@@ -4674,7 +4682,7 @@ def add_suffix(self: NDFrameT, suffix: str) -> NDFrameT:
         # expected "NDFrameT")
         # error: Argument 1 to "rename" of "NDFrame" has incompatible type
         # "**Dict[str, partial[str]]"; expected "Union[str, int, None]"
-        return self._rename(**mapper)  # type: ignore[return-value, arg-type]
+        return self._rename(**mapper, copy=copy)  # type: ignore[return-value, arg-type]
 
     @overload
     def sort_values(

pandas/tests/frame/methods/test_add_prefix_suffix.py

@@ -18,3 +18,56 @@ def test_add_prefix_suffix(float_frame):
     with_pct_suffix = float_frame.add_suffix("%")
     expected = Index([f"{c}%" for c in float_frame.columns])
     tm.assert_index_equal(with_pct_suffix.columns, expected)
+
+
+def test_add_prefix_suffix_copy(float_frame):
+    # GH#47934
+    ser = float_frame.iloc[0]
+
+    with_prefix = float_frame.add_prefix("foo#", copy=True)
+    expected = Index([f"foo#{c}" for c in float_frame.columns])
+    tm.assert_index_equal(with_prefix.columns, expected)
+    assert not any(
+        tm.shares_memory(float_frame.iloc[:, i], with_prefix.iloc[:, i])
+        for i in range(float_frame.shape[1])
+    )
+
+    ser_with_prefix = ser.add_prefix("foo#", copy=True)
+    tm.assert_index_equal(ser_with_prefix.index, expected)
+    assert not tm.shares_memory(ser_with_prefix, ser)
+
+    with_prefix = float_frame.add_prefix("foo#", copy=False)
+    expected = Index([f"foo#{c}" for c in float_frame.columns])
+    tm.assert_index_equal(with_prefix.columns, expected)
+    assert all(
+        tm.shares_memory(float_frame.iloc[:, i], with_prefix.iloc[:, i])
+        for i in range(float_frame.shape[1])
+    )
+
+    ser_with_prefix = ser.add_prefix("foo#", copy=False)
+    tm.assert_index_equal(ser_with_prefix.index, expected)
+    assert tm.shares_memory(ser_with_prefix, ser)
+
+    with_suffix = float_frame.add_suffix("#foo", copy=True)
+    expected = Index([f"{c}#foo" for c in float_frame.columns])
+    tm.assert_index_equal(with_suffix.columns, expected)
+    assert not any(
+        tm.shares_memory(float_frame.iloc[:, i], with_suffix.iloc[:, i])
+        for i in range(float_frame.shape[1])
+    )
+
+    ser_with_suffix = ser.add_suffix("#foo", copy=True)
+    tm.assert_index_equal(ser_with_suffix.index, expected)
+    assert not tm.shares_memory(ser_with_suffix, ser)
+
+    with_suffix = float_frame.add_suffix("#foo", copy=False)
+    expected = Index([f"{c}#foo" for c in float_frame.columns])
+    tm.assert_index_equal(with_suffix.columns, expected)
+    assert all(
+        tm.shares_memory(float_frame.iloc[:, i], with_suffix.iloc[:, i])
+        for i in range(float_frame.shape[1])
+    )
+
+    ser_with_suffix = ser.add_suffix("#foo", copy=False)
+    tm.assert_index_equal(ser_with_suffix.index, expected)
+    assert tm.shares_memory(ser_with_suffix, ser)