added deprecate_nonkeyword_arguments to function where

doc/source/whatsnew/v1.3.0.rst

@@ -649,7 +649,7 @@ Deprecations
 - Deprecated behavior of :meth:`DatetimeIndex.union` with mixed timezones; in a future version both will be cast to UTC instead of object dtype (:issue:`39328`)
 - Deprecated using ``usecols`` with out of bounds indices for ``read_csv`` with ``engine="c"`` (:issue:`25623`)
 - Deprecated passing arguments as positional (except for ``"method"``) in :meth:`DataFrame.interpolate` and :meth:`Series.interpolate` (:issue:`41485`)
-
+- Deprecated non-keyword arguments to ``where`` in :class:`NDFrame` (:issue:`41523`)
 .. ---------------------------------------------------------------------------
 
 

pandas/core/generic.py

@@ -61,6 +61,7 @@
     InvalidIndexError,
 )
 from pandas.util._decorators import (
+    deprecate_nonkeyword_arguments,
     doc,
     rewrite_axis_style_signature,
 )
@@ -9082,6 +9083,9 @@ def _where(
         name="where",
         name_other="mask",
     )
+    @deprecate_nonkeyword_arguments(
+        version=None, allowed_args=["self", "cond", "other"]
+    )
     def where(
         self,
         cond,

pandas/tests/frame/indexing/test_where.py

@@ -745,3 +745,11 @@ def test_where_bool_comparison():
         }
     )
     tm.assert_frame_equal(result, expected)
+
+
+def test_where():
+
+    s = Series(range(5))
+
+    with tm.assert_produces_warning(FutureWarning):
+        s.where(s > 1, 10, False)

pandas/tests/series/indexing/test_where.py

@@ -140,6 +140,9 @@ def test_where():
     rs = s2.where(cond[:3], -s2)
     tm.assert_series_equal(rs, expected)
 
+    with tm.assert_produces_warning(FutureWarning):
+        s.where(s > 1, 10, False)
+
 
 def test_where_error():
     s = Series(np.random.randn(5))