BUG: wrap all supported inplace methods to avoid making a copy (pandas-dev#12962) (pandas-dev#17589)

Author: dkamm

doc/source/whatsnew/v0.21.0.txt

@@ -646,6 +646,7 @@ PyPy
 
 Other
 ^^^^^
+- Bug where some inplace operators were not being wrapped and produced a copy when invoked (:issue:`12962`)
 - Bug in :func:`eval` where the ``inplace`` parameter was being incorrectly handled (:issue:`16732`)
 <<<<<<< HEAD
 - The ``Series`` constructor with no arguments would have an index like ``Index([], dtype='object')`` instead of ``RangeIndex(start=0, stop=0, step=1)``

pandas/core/ops.py

@@ -186,8 +186,10 @@ def add_special_arithmetic_methods(cls, arith_method=None,
     arith_method : function (optional)
         factory for special arithmetic methods, with op string:
         f(op, name, str_rep, default_axis=None, fill_zeros=None, **eval_kwargs)
-    comp_method : function, optional,
+    comp_method : function (optional)
         factory for rich comparison - signature: f(op, name, str_rep)
+    bool_method : function (optional)
+        factory for boolean methods - signature: f(op, name, str_rep)
     use_numexpr : bool, default True
         whether to accelerate with numexpr, defaults to True
     force : bool, default False
@@ -234,9 +236,16 @@ def f(self, other):
              __isub__=_wrap_inplace_method(new_methods["__sub__"]),
              __imul__=_wrap_inplace_method(new_methods["__mul__"]),
              __itruediv__=_wrap_inplace_method(new_methods["__truediv__"]),
-             __ipow__=_wrap_inplace_method(new_methods["__pow__"]), ))
+             __ifloordiv__=_wrap_inplace_method(new_methods["__floordiv__"]),
+             __imod__=_wrap_inplace_method(new_methods["__mod__"]),
+             __ipow__=_wrap_inplace_method(new_methods["__pow__"])))
     if not compat.PY3:
-        new_methods["__idiv__"] = new_methods["__div__"]
+        new_methods["__idiv__"] = _wrap_inplace_method(new_methods["__div__"])
+    if bool_method:
+        new_methods.update(
+            dict(__iand__=_wrap_inplace_method(new_methods["__and__"]),
+                 __ior__=_wrap_inplace_method(new_methods["__or__"]),
+                 __ixor__=_wrap_inplace_method(new_methods["__xor__"])))
 
     add_methods(cls, new_methods=new_methods, force=force, select=select,
                 exclude=exclude)

pandas/tests/frame/test_operators.py

@@ -1167,6 +1167,33 @@ def test_inplace_ops_identity(self):
         assert_frame_equal(df2, expected)
         assert df._data is df2._data
 
+    @pytest.mark.parametrize('op', ['add', 'and', 'div', 'floordiv', 'mod',
+                                    'mul', 'or', 'pow', 'sub', 'truediv',
+                                    'xor'])
+    def test_inplace_ops_identity2(self, op):
+
+        if compat.PY3 and op == 'div':
+            return
+
+        df = DataFrame({'a': [1., 2., 3.],
+                        'b': [1, 2, 3]})
+
+        operand = 2
+        if op in ('and', 'or', 'xor'):
+            # cannot use floats for boolean ops
+            df['a'] = [True, False, True]
+
+        df_copy = df.copy()
+        iop = '__i{}__'.format(op)
+        op = '__{}__'.format(op)
+
+        # no id change and value is correct
+        getattr(df, iop)(operand)
+        expected = getattr(df_copy, op)(operand)
+        assert_frame_equal(df, expected)
+        expected = id(df)
+        assert id(df) == expected
+
     def test_alignment_non_pandas(self):
         index = ['A', 'B', 'C']
         columns = ['X', 'Y', 'Z']