Fix inplace accessors (Issue #282)

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)
 --------------------

pint_pandas/pint_array.py

@@ -1355,13 +1355,21 @@ class DelegatedScalarProperty(DelegatedProperty):
 
 
 class DelegatedMethod(Delegated):
+    reinitialize = False
+
     def __get__(self, obj, type=None):
         index = object.__getattribute__(obj, "_index")
         name = object.__getattribute__(obj, "_name")
         method = getattr(object.__getattribute__(obj, "quantity"), self.name)
 
         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(
@@ -1377,6 +1385,11 @@ class DelegatedScalarMethod(DelegatedMethod):
     to_series = False
 
 
+class DelegatedInplaceMethod(DelegatedMethod):
+    to_series = False
+    reinitialize = True
+
+
 for attr in [
     "debug_used",
     "dimensionality",
@@ -1395,16 +1408,19 @@ 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",

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",