ENH: Move SettingWithCopyWarning to error/__init__.py per GH27656

doc/source/reference/testing.rst

@@ -42,6 +42,7 @@ Exceptions and warnings
    errors.ParserWarning
    errors.PerformanceWarning
    errors.SettingWithCopyError
+   errors.SettingWithCopyWarning
    errors.SpecificationError
    errors.UnsortedIndexError
    errors.UnsupportedFunctionCall

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`, :class:`SpecificationError`, and :class:`SettingWithCopyError` are now exposed in ``pandas.errors`` (:issue:`27656`)
+- :class:`DataError`, :class:`SpecificationError`, :class:`SettingWithCopyError`, and :class:`SettingWithCopyWarning` 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 SettingWithCopyWarning(Warning):
-    pass
-
-
 def flatten(line):
     """
     Flatten an arbitrarily nested sequence.

pandas/core/generic.py

@@ -70,6 +70,7 @@
     AbstractMethodError,
     InvalidIndexError,
     SettingWithCopyError,
+    SettingWithCopyWarning,
 )
 from pandas.util._decorators import (
     deprecate_kwarg,
@@ -3952,7 +3953,7 @@ def _check_setitem_copy(self, t="setting", force=False):
         if value == "raise":
             raise SettingWithCopyError(t)
         elif value == "warn":
-            warnings.warn(t, com.SettingWithCopyWarning, stacklevel=find_stack_level())
+            warnings.warn(t, SettingWithCopyWarning, stacklevel=find_stack_level())
 
     def __delitem__(self, key) -> None:
         """

pandas/errors/__init__.py

@@ -275,11 +275,11 @@ class SettingWithCopyError(ValueError):
     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 on eveluation order,
+    see :ref:`the user guide<indexing.evaluation_order>`.
 
-    For more information, see 'Indexing view versus copy' on
-    https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html
+    For more information on view vs. copy,
+    see :ref:`the user guide<indexing.view_versus_copy>`.
 
     Examples
     --------
@@ -288,3 +288,23 @@ class SettingWithCopyError(ValueError):
     >>> df.loc[0:3]['A'] = 'a' # doctest: +SKIP
     ... # SettingWithCopyError: A value is trying to be set on a copy of a...
     """
+
+
+class SettingWithCopyWarning(Warning):
+    """
+    Warning is raised when trying to set on a copied slice from a dataframe and
+    the mode.chained_assignment is set to 'warn.' 'Warn' is the default option.
+    This can happen unintentionally when chained indexing.
+
+    For more information on eveluation order,
+    see :ref:`the user guide<indexing.evaluation_order>`.
+
+    For more information on view vs. copy,
+    see :ref:`the user guide<indexing.view_versus_copy>`.
+
+    Examples
+    --------
+    >>> df = pd.DataFrame({'A': [1, 1, 1, 2, 2]}, columns=['A'])
+    >>> df.loc[0:3]['A'] = 'a' # doctest: +SKIP
+    ... # SettingWithCopyWarning: A value is trying to be set on a copy of a...
+    """

pandas/tests/copy_view/test_indexing.py

@@ -1,13 +1,14 @@
 import numpy as np
 import pytest
 
+from pandas.errors import SettingWithCopyWarning
+
 import pandas as pd
 from pandas import (
     DataFrame,
     Series,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 from pandas.tests.copy_view.util import get_array
 
 # -----------------------------------------------------------------------------
@@ -31,7 +32,7 @@ def test_subset_column_selection(using_copy_on_write):
         assert not np.shares_memory(get_array(subset, "a"), get_array(df, "a"))
         # INFO this no longer raise warning since pandas 1.4
         # with pd.option_context("chained_assignment", "warn"):
-        #     with tm.assert_produces_warning(com.SettingWithCopyWarning):
+        #     with tm.assert_produces_warning(SettingWithCopyWarning):
         subset.iloc[0, 0] = 0
 
     assert not np.shares_memory(get_array(subset, "a"), get_array(df, "a"))
@@ -80,7 +81,7 @@ def test_subset_row_slice(using_copy_on_write):
     else:
         # INFO this no longer raise warning since pandas 1.4
         # with pd.option_context("chained_assignment", "warn"):
-        #     with tm.assert_produces_warning(com.SettingWithCopyWarning):
+        #     with tm.assert_produces_warning(SettingWithCopyWarning):
         subset.iloc[0, 0] = 0
 
     subset._mgr._verify_integrity()
@@ -119,7 +120,7 @@ def test_subset_column_slice(using_copy_on_write, using_array_manager, dtype):
 
     else:
         # we only get a warning in case of a single block
-        warn = com.SettingWithCopyWarning if single_block else None
+        warn = SettingWithCopyWarning if single_block else None
         with pd.option_context("chained_assignment", "warn"):
             with tm.assert_produces_warning(warn):
                 subset.iloc[0, 0] = 0
@@ -252,7 +253,7 @@ def test_subset_set_with_row_indexer(indexer_si, indexer, using_copy_on_write):
         indexer_si(subset)[indexer] = 0
     else:
         # INFO iloc no longer raises warning since pandas 1.4
-        warn = com.SettingWithCopyWarning if indexer_si is tm.setitem else None
+        warn = SettingWithCopyWarning if indexer_si is tm.setitem else None
         with pd.option_context("chained_assignment", "warn"):
             with tm.assert_produces_warning(warn):
                 indexer_si(subset)[indexer] = 0
@@ -282,7 +283,7 @@ def test_subset_set_with_mask(using_copy_on_write):
         subset[mask] = 0
     else:
         with pd.option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 subset[mask] = 0
 
     expected = DataFrame(
@@ -309,7 +310,7 @@ def test_subset_set_column(using_copy_on_write):
         subset["a"] = np.array([10, 11], dtype="int64")
     else:
         with pd.option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 subset["a"] = np.array([10, 11], dtype="int64")
 
     subset._mgr._verify_integrity()
@@ -340,7 +341,7 @@ def test_subset_set_column_with_loc(using_copy_on_write, using_array_manager, dt
             # warnings and only assert the SettingWithCopyWarning
             raise_on_extra_warnings = False if using_array_manager else True
             with tm.assert_produces_warning(
-                com.SettingWithCopyWarning,
+                SettingWithCopyWarning,
                 raise_on_extra_warnings=raise_on_extra_warnings,
             ):
                 subset.loc[:, "a"] = np.array([10, 11], dtype="int64")
@@ -377,7 +378,7 @@ def test_subset_set_column_with_loc2(using_copy_on_write, using_array_manager):
             # warnings and only assert the SettingWithCopyWarning
             raise_on_extra_warnings = False if using_array_manager else True
             with tm.assert_produces_warning(
-                com.SettingWithCopyWarning,
+                SettingWithCopyWarning,
                 raise_on_extra_warnings=raise_on_extra_warnings,
             ):
                 subset.loc[:, "a"] = 0
@@ -410,7 +411,7 @@ def test_subset_set_columns(using_copy_on_write, dtype):
         subset[["a", "c"]] = 0
     else:
         with pd.option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 subset[["a", "c"]] = 0
 
     subset._mgr._verify_integrity()
@@ -443,7 +444,7 @@ def test_subset_set_with_column_indexer(
             # The (i)loc[:, col] inplace deprecation gets triggered here, ignore those
             # warnings and only assert the SettingWithCopyWarning
             with tm.assert_produces_warning(
-                com.SettingWithCopyWarning, raise_on_extra_warnings=False
+                SettingWithCopyWarning, raise_on_extra_warnings=False
             ):
                 subset.loc[:, indexer] = 0
 
@@ -580,7 +581,7 @@ def test_column_as_series(using_copy_on_write, using_array_manager):
         s[0] = 0
     else:
         with pd.option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 s[0] = 0
 
     expected = Series([0, 2, 3], name="a")
@@ -607,7 +608,7 @@ def test_column_as_series_set_with_upcast(using_copy_on_write, using_array_manag
         s[0] = "foo"
     else:
         with pd.option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 s[0] = "foo"
 
     expected = Series(["foo", 2, 3], dtype=object, name="a")

pandas/tests/indexing/test_chaining_and_caching.py

@@ -3,7 +3,10 @@
 import numpy as np
 import pytest
 
-from pandas.errors import SettingWithCopyError
+from pandas.errors import (
+    SettingWithCopyError,
+    SettingWithCopyWarning,
+)
 import pandas.util._test_decorators as td
 
 import pandas as pd
@@ -15,7 +18,6 @@
     option_context,
 )
 import pandas._testing as tm
-import pandas.core.common as com
 
 msg = "A value is trying to be set on a copy of a slice from a DataFrame"
 
@@ -415,7 +417,7 @@ def test_setting_with_copy_bug_no_warning(self):
     def test_detect_chained_assignment_warnings_errors(self):
         df = DataFrame({"A": ["aaa", "bbb", "ccc"], "B": [1, 2, 3]})
         with option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 df.loc[0]["A"] = 111
 
         with option_context("chained_assignment", "raise"):
@@ -427,7 +429,7 @@ def test_detect_chained_assignment_warnings_filter_and_dupe_cols(self):
         with option_context("chained_assignment", "warn"):
             df = DataFrame([[1, 2, 3], [4, 5, 6], [7, 8, -9]], columns=["a", "a", "c"])
 
-            with tm.assert_produces_warning(com.SettingWithCopyWarning):
+            with tm.assert_produces_warning(SettingWithCopyWarning):
                 df.c.loc[df.c > 0] = None
 
             expected = DataFrame(
@@ -441,7 +443,7 @@ def test_detect_chained_assignment_warning_stacklevel(self, rhs):
         df = DataFrame(np.arange(25).reshape(5, 5))
         chained = df.loc[:3]
         with option_context("chained_assignment", "warn"):
-            with tm.assert_produces_warning(com.SettingWithCopyWarning) as t:
+            with tm.assert_produces_warning(SettingWithCopyWarning) as t:
                 chained[2] = rhs
                 assert t[0].filename == __file__
 

pandas/tests/test_errors.py

@@ -22,6 +22,7 @@
         "DataError",
         "SpecificationError",
         "SettingWithCopyError",
+        "SettingWithCopyWarning",
     ],
 )
 def test_exception_importable(exc):