ENH: Move SettingWithCopyError to error/__init__.py per GH27656 (#47151)

* ENH: Move SettingWithCopyError to error/__init__.py per GH27656 * ENH: add exception to test_exception_importable

Author: dataxerik

doc/source/reference/testing.rst

@@ -41,6 +41,7 @@ Exceptions and warnings
  errors.ParserError
  errors.ParserWarning
  errors.PerformanceWarning
+ errors.SettingWithCopyError
  errors.SpecificationError
  errors.UnsortedIndexError
  errors.UnsupportedFunctionCall

doc/source/user_guide/indexing.rst

@@ -1885,7 +1885,7 @@ chained indexing expression, you can set the :ref:`option <options>`
 ``mode.chained_assignment`` to one of these values:
 
 * ``'warn'``, the default, means a ``SettingWithCopyWarning`` is printed.
-* ``'raise'`` means pandas will raise a ``SettingWithCopyException``
+* ``'raise'`` means pandas will raise a ``SettingWithCopyError``
  you have to deal with.
 * ``None`` will suppress the warnings entirely.
 
@@ -1953,7 +1953,7 @@ Last, the subsequent example will **not** work at all, and so should be avoided:
  >>> dfd.loc[0]['a'] = 1111
  Traceback (most recent call last)
  ...
- SettingWithCopyException:
+ SettingWithCopyError:
  A value is trying to be set on a copy of a slice from a DataFrame.
  Try using .loc[row_index,col_indexer] = value instead
 

doc/source/whatsnew/v1.5.0.rst

@@ -151,7 +151,7 @@ Other enhancements
 - A :class:`errors.PerformanceWarning` is now thrown when using ``string[pyarrow]`` dtype with methods that don't dispatch to ``pyarrow.compute`` methods (:issue:`42613`)
 - Added ``numeric_only`` argument to :meth:`Resampler.sum`, :meth:`Resampler.prod`, :meth:`Resampler.min`, :meth:`Resampler.max`, :meth:`Resampler.first`, and :meth:`Resampler.last` (:issue:`46442`)
 - ``times`` argument in :class:`.ExponentialMovingWindow` now accepts ``np.timedelta64`` (:issue:`47003`)
-- :class:`DataError` and :class:`SpecificationError` are now exposed in ``pandas.errors`` (:issue:`27656`)
+- :class:`DataError`, :class:`SpecificationError`, and :class:`SettingWithCopyError` are now exposed in ``pandas.errors`` (:issue:`27656`)
 
 .. ---------------------------------------------------------------------------
 .. _whatsnew_150.notable_bug_fixes:

pandas/core/common.py

@@ -58,10 +58,6 @@
  from pandas import Index
 
 
-class SettingWithCopyError(ValueError):
- pass
-
-
 class SettingWithCopyWarning(Warning):
  pass
 

pandas/core/generic.py

@@ -69,6 +69,7 @@
 from pandas.errors import (
  AbstractMethodError,
  InvalidIndexError,
+ SettingWithCopyError,
 )
 from pandas.util._decorators import (
  deprecate_kwarg,
@@ -3949,7 +3950,7 @@ def _check_setitem_copy(self, t="setting", force=False):
  )
 
  if value == "raise":
- raise com.SettingWithCopyError(t)
+ raise SettingWithCopyError(t)
  elif value == "warn":
  warnings.warn(t, com.SettingWithCopyWarning, stacklevel=find_stack_level())
 

pandas/errors/__init__.py

@@ -267,3 +267,24 @@ class SpecificationError(Exception):
  >>> df.groupby('A').agg(['min', 'min']) # doctest: +SKIP
  ... # SpecificationError: nested renamer is not supported
  """
+
+
+class SettingWithCopyError(ValueError):
+ """
+ Exception is raised when trying to set on a copied slice from a dataframe and
+ the mode.chained_assignment is set to 'raise.' This can happen unintentionally
+ when chained indexing.
+
+ For more information, see 'Evaluation order matters' on
+ https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html
+
+ For more information, see 'Indexing view versus copy' on
+ https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html
+
+ Examples
+ --------
+ >>> pd.options.mode.chained_assignment = 'raise'
+ >>> df = pd.DataFrame({'A': [1, 1, 1, 2, 2]}, columns=['A'])
+ >>> df.loc[0:3]['A'] = 'a' # doctest: +SKIP
+ ... # SettingWithCopyError: A value is trying to be set on a copy of a...
+ """

pandas/tests/frame/indexing/test_indexing.py

@@ -8,7 +8,10 @@
 import pytest
 
 from pandas._libs import iNaT
-from pandas.errors import InvalidIndexError
+from pandas.errors import (
+ InvalidIndexError,
+ SettingWithCopyError,
+)
 import pandas.util._test_decorators as td
 
 from pandas.core.dtypes.common import is_integer
@@ -27,7 +30,6 @@
  notna,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 
 # We pass through a TypeError raised by numpy
 _slice_msg = "slice indices must be integers or None or have an __index__ method"
@@ -303,7 +305,7 @@ def test_setitem(self, float_frame):
  smaller = float_frame[:2]
 
  msg = r"\nA value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  smaller["col10"] = ["1", "2"]
 
  assert smaller["col10"].dtype == np.object_
@@ -546,7 +548,7 @@ def test_fancy_getitem_slice_mixed(self, float_frame, float_string_frame):
  assert np.shares_memory(sliced["C"]._values, float_frame["C"]._values)
 
  msg = r"\nA value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  sliced.loc[:, "C"] = 4.0
 
  assert (float_frame["C"] == 4).all()
@@ -1003,7 +1005,7 @@ def test_iloc_row_slice_view(self, using_array_manager):
  assert np.shares_memory(df[2], subset[2])
 
  msg = r"\nA value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  subset.loc[:, 2] = 0.0
 
  exp_col = original[2].copy()
@@ -1046,7 +1048,7 @@ def test_iloc_col_slice_view(self, using_array_manager):
 
  # and that we are setting a copy
  msg = r"\nA value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  subset.loc[:, 8] = 0.0
 
  assert (df[8] == 0).all()

pandas/tests/frame/indexing/test_xs.py

@@ -3,6 +3,8 @@
 import numpy as np
 import pytest
 
+from pandas.errors import SettingWithCopyError
+
 from pandas import (
  DataFrame,
  Index,
@@ -12,7 +14,6 @@
  concat,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 
 from pandas.tseries.offsets import BDay
 
@@ -120,7 +121,7 @@ def test_xs_view(self, using_array_manager):
  # INFO(ArrayManager) with ArrayManager getting a row as a view is
  # not possible
  msg = r"\nA value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  dm.xs(2)[:] = 20
  assert not (dm.xs(2) == 20).any()
  else:
@@ -183,7 +184,7 @@ def test_xs_setting_with_copy_error(self, multiindex_dataframe_random_data):
  # setting this will give a SettingWithCopyError
  # as we are trying to write a view
  msg = "A value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  result[:] = 10
 
  def test_xs_setting_with_copy_error_multiple(self, four_level_index_dataframe):
@@ -194,7 +195,7 @@ def test_xs_setting_with_copy_error_multiple(self, four_level_index_dataframe):
  # setting this will give a SettingWithCopyError
  # as we are trying to write a view
  msg = "A value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  result[:] = 10
 
  @pytest.mark.parametrize("key, level", [("one", "second"), (["one"], ["second"])])

pandas/tests/indexing/multiindex/test_chaining_and_caching.py

@@ -1,6 +1,7 @@
 import numpy as np
 import pytest
 
+from pandas.errors import SettingWithCopyError
 import pandas.util._test_decorators as td
 
 from pandas import (
@@ -9,7 +10,6 @@
  Series,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 
 
 def test_detect_chained_assignment():
@@ -30,7 +30,7 @@ def test_detect_chained_assignment():
  zed = DataFrame(events, index=["a", "b"], columns=multiind)
 
  msg = "A value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  zed["eyes"]["right"].fillna(value=555, inplace=True)
 
 

pandas/tests/indexing/multiindex/test_setitem.py

@@ -1,6 +1,7 @@
 import numpy as np
 import pytest
 
+from pandas.errors import SettingWithCopyError
 import pandas.util._test_decorators as td
 
 import pandas as pd
@@ -14,7 +15,6 @@
  notna,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 
 
 def assert_equal(a, b):
@@ -491,7 +491,7 @@ def test_frame_setitem_copy_raises(multiindex_dataframe_random_data):
  # will raise/warn as its chained assignment
  df = multiindex_dataframe_random_data.T
  msg = "A value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  df["foo"]["one"] = 2
 
 
@@ -500,7 +500,7 @@ def test_frame_setitem_copy_no_write(multiindex_dataframe_random_data):
  expected = frame
  df = frame.copy()
  msg = "A value is trying to be set on a copy of a slice from a DataFrame"
- with pytest.raises(com.SettingWithCopyError, match=msg):
+ with pytest.raises(SettingWithCopyError, match=msg):
  df["foo"]["one"] = 2
 
  result = df