DEPR: verify_integrity in DataFrame.set_index (#63033)

Author: jbrockmendel

doc/source/whatsnew/v3.0.0.rst

@@ -798,6 +798,7 @@ Other Deprecations
 - Deprecated lowercase strings ``w``, ``w-mon``, ``w-tue``, etc. denoting frequencies in :class:`Week` in favour of ``W``, ``W-MON``, ``W-TUE``, etc. (:issue:`58998`)
 - Deprecated parameter ``method`` in :meth:`DataFrame.reindex_like` / :meth:`Series.reindex_like` (:issue:`58667`)
 - Deprecated strings ``w``, ``d``, ``MIN``, ``MS``, ``US`` and ``NS`` denoting units in :class:`Timedelta` in favour of ``W``, ``D``, ``min``, ``ms``, ``us`` and ``ns`` (:issue:`59051`)
+- Deprecated the 'verify_integrity' keyword in :meth:`DataFrame.set_index`; directly check the result for ``obj.index.is_unique`` instead (:issue:`62919`)
 - Deprecated the ``arg`` parameter of ``Series.map``; pass the added ``func`` argument instead. (:issue:`61260`)
 - Deprecated using ``epoch`` date format in :meth:`DataFrame.to_json` and :meth:`Series.to_json`, use ``iso`` instead. (:issue:`57063`)
 - Deprecated allowing ``fill_value`` that cannot be held in the original dtype (excepting NA values for integer and bool dtypes) in :meth:`Series.unstack` and :meth:`DataFrame.unstack` (:issue:`12189`, :issue:`53868`)

pandas/core/frame.py

@@ -6225,7 +6225,7 @@ def set_index(
         drop: bool = ...,
         append: bool = ...,
         inplace: Literal[False] = ...,
-        verify_integrity: bool = ...,
+        verify_integrity: bool | lib.NoDefault = ...,
     ) -> DataFrame: ...
 
     @overload
@@ -6236,7 +6236,7 @@ def set_index(
         drop: bool = ...,
         append: bool = ...,
         inplace: Literal[True],
-        verify_integrity: bool = ...,
+        verify_integrity: bool | lib.NoDefault = ...,
     ) -> None: ...
 
     def set_index(
@@ -6246,7 +6246,7 @@ def set_index(
         drop: bool = True,
         append: bool = False,
         inplace: bool = False,
-        verify_integrity: bool = False,
+        verify_integrity: bool | lib.NoDefault = lib.no_default,
     ) -> DataFrame | None:
         """
         Set the DataFrame index using existing columns.
@@ -6276,6 +6276,8 @@ def set_index(
             necessary. Setting to False will improve the performance of this
             method.
 
+            .. deprecated:: 3.0.0
+
         Returns
         -------
         DataFrame or None
@@ -6362,6 +6364,18 @@ def set_index(
         2013    84
         2014    31
         """
+        if verify_integrity is not lib.no_default:
+            # GH#62919
+            warnings.warn(
+                "The 'verify_integrity' keyword in DataFrame.set_index is "
+                "deprecated and will be removed in a future version. "
+                "Directly check the result.index.is_unique instead.",
+                Pandas4Warning,
+                stacklevel=find_stack_level(),
+            )
+        else:
+            verify_integrity = False
+
         inplace = validate_bool_kwarg(inplace, "inplace")
         self._check_inplace_and_allows_duplicate_labels(inplace)
         if not isinstance(keys, list):

pandas/tests/frame/methods/test_set_index.py

@@ -10,6 +10,8 @@
 import numpy as np
 import pytest
 
+from pandas.errors import Pandas4Warning
+
 from pandas import (
     Categorical,
     CategoricalIndex,
@@ -547,11 +549,14 @@ class TestSetIndexInvalid:
     def test_set_index_verify_integrity(self, frame_of_index_cols):
         df = frame_of_index_cols
 
+        msg = "The 'verify_integrity' keyword in DataFrame.set_index"
         with pytest.raises(ValueError, match="Index has duplicate keys"):
-            df.set_index("A", verify_integrity=True)
+            with tm.assert_produces_warning(Pandas4Warning, match=msg):
+                df.set_index("A", verify_integrity=True)
         # with MultiIndex
         with pytest.raises(ValueError, match="Index has duplicate keys"):
-            df.set_index([df["A"], df["A"]], verify_integrity=True)
+            with tm.assert_produces_warning(Pandas4Warning, match=msg):
+                df.set_index([df["A"], df["A"]], verify_integrity=True)
 
     @pytest.mark.parametrize("append", [True, False])
     @pytest.mark.parametrize("drop", [True, False])