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

Author: dkamm

doc/source/whatsnew/v0.21.0.txt

@@ -646,4 +646,5 @@ 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`)

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']