From 32dd2553d9a40695f820830b82bd97c436e6ac2c Mon Sep 17 00:00:00 2001
From: Etienne Bresciani <53166244+etiennebresciani@users.noreply.github.com>
Date: Wed, 13 Aug 2025 10:45:53 -0400
Subject: [PATCH 1/2] Fix inplace accessor methods (#282)

- Fix inplace accessor methods (ito(), etc.; Issue #282)
- Fix corresponding tests, which were wrong
---
 CHANGES                                       |  1 +
 pint_pandas/pint_array.py                     | 23 +++++++++++++++----
 .../testsuite/test_pandas_interface.py        |  5 ++--
 3 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/CHANGES b/CHANGES
index e7f7e063..1362ef0f 100644
--- a/CHANGES
+++ b/CHANGES
@@ -7,6 +7,7 @@ pint-pandas Changelog
 
 - `Dataframe.pint.quantify` and `Dataframe.pint.dequantify` will now accept and return single row headers,
   allowing it to parse column names such as `torque [lbf in]`.
+- Fix inplace accessor methods (ito(), etc.; Issue #282)
 
 0.7.1 (2025-01-06)
 --------------------
diff --git a/pint_pandas/pint_array.py b/pint_pandas/pint_array.py
index 3468c8c2..af3c2f16 100644
--- a/pint_pandas/pint_array.py
+++ b/pint_pandas/pint_array.py
@@ -1355,6 +1355,8 @@ class DelegatedScalarProperty(DelegatedProperty):
 
 
 class DelegatedMethod(Delegated):
+    reinitialize = False
+
     def __get__(self, obj, type=None):
         index = object.__getattribute__(obj, "_index")
         name = object.__getattribute__(obj, "_name")
@@ -1362,6 +1364,12 @@ def __get__(self, obj, type=None):
 
         def delegated_method(*args, **kwargs):
             result = method(*args, **kwargs)
+            if self.reinitialize:
+                q = object.__getattribute__(obj, "quantity")
+                values = pd.array(q.m)
+                dtype = PintType(units=q.units, subdtype=ddtypemap[q.dtype])
+                po = object.__getattribute__(obj, "pandas_obj")
+                po.__init__(values, dtype=dtype)
             if self.to_series:
                 if isinstance(result, _Quantity):
                     result = PintArray.from_1darray_quantity(
@@ -1376,6 +1384,10 @@ def delegated_method(*args, **kwargs):
 class DelegatedScalarMethod(DelegatedMethod):
     to_series = False
 
+class DelegatedInplaceMethod(DelegatedMethod):
+    to_series = False
+    reinitialize = True
+
 
 for attr in [
     "debug_used",
@@ -1395,16 +1407,19 @@ class DelegatedScalarMethod(DelegatedMethod):
     "check",
     "compatible_units",
     "format_babel",
+    "plus_minus",
+    "to_tuple",
+    "tolist",
+]:
+    setattr(PintSeriesAccessor, attr, DelegatedScalarMethod(attr))
+for attr in [
     "ito",
     "ito_base_units",
     "ito_reduced_units",
     "ito_root_units",
-    "plus_minus",
     "put",
-    "to_tuple",
-    "tolist",
 ]:
-    setattr(PintSeriesAccessor, attr, DelegatedScalarMethod(attr))
+    setattr(PintSeriesAccessor, attr, DelegatedInplaceMethod(attr))
 for attr in [
     "clip",
     "from_tuple",
diff --git a/pint_pandas/testsuite/test_pandas_interface.py b/pint_pandas/testsuite/test_pandas_interface.py
index 858210be..86bad41a 100644
--- a/pint_pandas/testsuite/test_pandas_interface.py
+++ b/pint_pandas/testsuite/test_pandas_interface.py
@@ -377,8 +377,9 @@ def test_series_inplace_method_accessors(self, data, attr_args):
 
         s = pd.Series(deepcopy(data))
         getattr(s.pint, attr)(*args)
-        getattr(data.quantity, attr)(*args)
-        assert all(s.values == data)
+        q = data.quantity
+        getattr(q, attr)(*args)
+        assert all(s.values == q)
 
     @pytest.mark.parametrize(
         "attr_args",

From f56641ba1f2c57834e5a45808629e0ad52067d35 Mon Sep 17 00:00:00 2001
From: Etienne Bresciani <53166244+etiennebresciani@users.noreply.github.com>
Date: Wed, 13 Aug 2025 10:59:17 -0400
Subject: [PATCH 2/2] Fix code format

Fix code format (missing blank line)
---
 pint_pandas/pint_array.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/pint_pandas/pint_array.py b/pint_pandas/pint_array.py
index af3c2f16..b061ecb1 100644
--- a/pint_pandas/pint_array.py
+++ b/pint_pandas/pint_array.py
@@ -1384,6 +1384,7 @@ def delegated_method(*args, **kwargs):
 class DelegatedScalarMethod(DelegatedMethod):
     to_series = False
 
+
 class DelegatedInplaceMethod(DelegatedMethod):
     to_series = False
     reinitialize = True