diff --git a/pandas/core/frame.py b/pandas/core/frame.py
index 54ee5ed2f35d1..879a6a2a034d6 100644
--- a/pandas/core/frame.py
+++ b/pandas/core/frame.py
@@ -98,7 +98,6 @@
)
from pandas.core.dtypes.cast import (
- LossySetitemError,
can_hold_element,
construct_1d_arraylike_from_scalar,
construct_2d_arraylike_from_scalar,
@@ -3945,17 +3944,18 @@ def _set_value(
"""
try:
if takeable:
- series = self._ixs(col, axis=1)
- loc = index
+ icol = col
+ iindex = cast(int, index)
else:
- series = self._get_item_cache(col)
- loc = self.index.get_loc(index)
-
- # setitem_inplace will do validation that may raise TypeError,
- # ValueError, or LossySetitemError
- series._mgr.setitem_inplace(loc, value)
-
- except (KeyError, TypeError, ValueError, LossySetitemError):
+ icol = self.columns.get_loc(col)
+ iindex = self.index.get_loc(index)
+ self._mgr.column_setitem(icol, iindex, value)
+ self._clear_item_cache()
+
+ except (KeyError, TypeError, ValueError):
+ # get_loc might raise a KeyError for missing labels (falling back
+ # to (i)loc will do expansion of the index)
+ # column_setitem will do validation that may raise TypeError or ValueError
# set using a non-recursive method & reset the cache
if takeable:
self.iloc[index, col] = value
diff --git a/pandas/core/indexers/__init__.py b/pandas/core/indexers/__init__.py
index 86ec36144b134..6431f12a08dc8 100644
--- a/pandas/core/indexers/__init__.py
+++ b/pandas/core/indexers/__init__.py
@@ -4,7 +4,6 @@
check_setitem_lengths,
deprecate_ndim_indexing,
is_empty_indexer,
- is_exact_shape_match,
is_list_like_indexer,
is_scalar_indexer,
is_valid_positional_slice,
@@ -23,7 +22,6 @@
"check_setitem_lengths",
"validate_indices",
"maybe_convert_indices",
- "is_exact_shape_match",
"length_of_indexer",
"deprecate_ndim_indexing",
"unpack_1tuple",
diff --git a/pandas/core/indexers/utils.py b/pandas/core/indexers/utils.py
index 8c38341e02e34..f098066d1c7d7 100644
--- a/pandas/core/indexers/utils.py
+++ b/pandas/core/indexers/utils.py
@@ -11,10 +11,7 @@
import numpy as np
-from pandas._typing import (
- AnyArrayLike,
- ArrayLike,
-)
+from pandas._typing import AnyArrayLike
from pandas.util._exceptions import find_stack_level
from pandas.core.dtypes.common import (
@@ -294,27 +291,6 @@ def maybe_convert_indices(indices, n: int, verify: bool = True):
# Unsorted
-def is_exact_shape_match(target: ArrayLike, value: ArrayLike) -> bool:
- """
- Is setting this value into this target overwriting the entire column?
-
- Parameters
- ----------
- target : np.ndarray or ExtensionArray
- value : np.ndarray or ExtensionArray
-
- Returns
- -------
- bool
- """
- return (
- len(value.shape) > 0
- and len(target.shape) > 0
- and value.shape[0] == target.shape[0]
- and value.size == target.size
- )
-
-
def length_of_indexer(indexer, target=None) -> int:
"""
Return the expected length of target[indexer]
diff --git a/pandas/core/indexing.py b/pandas/core/indexing.py
index 849e7b6921c4f..20ac0fedc28d1 100644
--- a/pandas/core/indexing.py
+++ b/pandas/core/indexing.py
@@ -53,7 +53,6 @@
from pandas.core.indexers import (
check_array_indexer,
is_empty_indexer,
- is_exact_shape_match,
is_list_like_indexer,
is_scalar_indexer,
length_of_indexer,
@@ -1951,8 +1950,7 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
"""
pi = plane_indexer
- ser = self.obj._ixs(loc, axis=1)
- orig_values = ser._values
+ orig_values = self.obj._get_column_array(loc)
# perform the equivalent of a setitem on the info axis
# as we have a null slice or a slice with full bounds
@@ -1963,7 +1961,8 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
pass
elif (
is_array_like(value)
- and is_exact_shape_match(ser, value)
+ and len(value.shape) > 0
+ and self.obj.shape[0] == value.shape[0]
and not is_empty_indexer(pi)
):
if is_list_like(pi):
@@ -1972,31 +1971,23 @@ def _setitem_single_column(self, loc: int, value, plane_indexer):
# in case of slice
value = value[pi]
else:
- # set the item, first attempting to operate inplace, then
- # falling back to casting if necessary; see
- # _whatsnew_130.notable_bug_fixes.setitem_column_try_inplace
-
- orig_values = ser._values
- ser._mgr = ser._mgr.setitem((pi,), value)
-
- if ser._values is orig_values:
- # The setitem happened inplace, so the DataFrame's values
- # were modified inplace.
- return
- self.obj._iset_item(loc, ser)
+ # set value into the column (first attempting to operate inplace, then
+ # falling back to casting if necessary)
+ self.obj._mgr.column_setitem(loc, plane_indexer, value)
+ self.obj._clear_item_cache()
return
# We will not operate in-place, but will attempt to in the future.
# To determine whether we need to issue a FutureWarning, see if the
# setting in-place would work, i.e. behavior will change.
- warn = can_hold_element(ser._values, value)
+ warn = can_hold_element(orig_values, value)
# Don't issue the warning yet, as we can still trim a few cases where
# behavior will not change.
self.obj._iset_item(loc, value)
if warn:
- new_values = self.obj._ixs(loc, axis=1)._values
+ new_values = self.obj._get_column_array(loc)
if (
isinstance(new_values, np.ndarray)
diff --git a/pandas/core/internals/array_manager.py b/pandas/core/internals/array_manager.py
index 0c16ddbbc21ab..ee6c183898079 100644
--- a/pandas/core/internals/array_manager.py
+++ b/pandas/core/internals/array_manager.py
@@ -36,6 +36,7 @@
is_datetime64_ns_dtype,
is_dtype_equal,
is_extension_array_dtype,
+ is_integer,
is_numeric_dtype,
is_object_dtype,
is_timedelta64_ns_dtype,
@@ -869,6 +870,21 @@ def iset(
self.arrays[mgr_idx] = value_arr
return
+ def column_setitem(self, loc: int, idx: int | slice | np.ndarray, value) -> None:
+ """
+ Set values ("setitem") into a single column (not setting the full column).
+
+ This is a method on the ArrayManager level, to avoid creating an
+ intermediate Series at the DataFrame level (`s = df[loc]; s[idx] = value`)
+ """
+ if not is_integer(loc):
+ raise TypeError("The column index should be an integer")
+ arr = self.arrays[loc]
+ mgr = SingleArrayManager([arr], [self._axes[0]])
+ new_mgr = mgr.setitem((idx,), value)
+ # update existing ArrayManager in-place
+ self.arrays[loc] = new_mgr.arrays[0]
+
def insert(self, loc: int, item: Hashable, value: ArrayLike) -> None:
"""
Insert item at selected position.
diff --git a/pandas/core/internals/managers.py b/pandas/core/internals/managers.py
index f530c58bbd0c0..7cccc9833de6b 100644
--- a/pandas/core/internals/managers.py
+++ b/pandas/core/internals/managers.py
@@ -1188,6 +1188,17 @@ def _iset_single(
self.blocks = new_blocks
return
+ def column_setitem(self, loc: int, idx: int | slice | np.ndarray, value) -> None:
+ """
+ Set values ("setitem") into a single column (not setting the full column).
+
+ This is a method on the BlockManager level, to avoid creating an
+ intermediate Series at the DataFrame level (`s = df[loc]; s[idx] = value`)
+ """
+ col_mgr = self.iget(loc)
+ new_mgr = col_mgr.setitem((idx,), value)
+ self.iset(loc, new_mgr._block.values, inplace=True)
+
def insert(self, loc: int, item: Hashable, value: ArrayLike) -> None:
"""
Insert item at selected position.
diff --git a/pandas/tests/frame/indexing/test_setitem.py b/pandas/tests/frame/indexing/test_setitem.py
index 75bef4f34c99e..cf6d351aa78a0 100644
--- a/pandas/tests/frame/indexing/test_setitem.py
+++ b/pandas/tests/frame/indexing/test_setitem.py
@@ -1099,8 +1099,6 @@ def test_setitem_partial_column_inplace(self, consolidate, using_array_manager):
# check setting occurred in-place
tm.assert_numpy_array_equal(zvals, expected.values)
assert np.shares_memory(zvals, df["z"]._values)
- if not consolidate:
- assert df["z"]._values is zvals
def test_setitem_duplicate_columns_not_inplace(self):
# GH#39510
diff --git a/pandas/tests/indexing/test_at.py b/pandas/tests/indexing/test_at.py
index a2f02378d061a..96c73b007cef3 100644
--- a/pandas/tests/indexing/test_at.py
+++ b/pandas/tests/indexing/test_at.py
@@ -10,6 +10,7 @@
CategoricalDtype,
CategoricalIndex,
DataFrame,
+ MultiIndex,
Series,
Timestamp,
)
@@ -96,6 +97,18 @@ def test_at_setitem_categorical_missing(self):
tm.assert_frame_equal(df, expected)
+ def test_at_setitem_multiindex(self):
+ df = DataFrame(
+ np.zeros((3, 2), dtype="int64"),
+ columns=MultiIndex.from_tuples([("a", 0), ("a", 1)]),
+ )
+ df.at[0, "a"] = 10
+ expected = DataFrame(
+ [[10, 10], [0, 0], [0, 0]],
+ columns=MultiIndex.from_tuples([("a", 0), ("a", 1)]),
+ )
+ tm.assert_frame_equal(df, expected)
+
class TestAtSetItemWithExpansion:
def test_at_setitem_expansion_series_dt64tz_value(self, tz_naive_fixture):
diff --git a/pandas/tests/indexing/test_partial.py b/pandas/tests/indexing/test_partial.py
index 3c57970d46bc9..938056902e745 100644
--- a/pandas/tests/indexing/test_partial.py
+++ b/pandas/tests/indexing/test_partial.py
@@ -266,7 +266,7 @@ def test_partial_setting(self):
with pytest.raises(IndexError, match=msg):
s.iat[3] = 5.0
- def test_partial_setting_frame(self):
+ def test_partial_setting_frame(self, using_array_manager):
df_orig = DataFrame(
np.arange(6).reshape(3, 2), columns=["A", "B"], dtype="int64"
)
@@ -279,6 +279,8 @@ def test_partial_setting_frame(self):
df.iloc[4, 2] = 5.0
msg = "index 2 is out of bounds for axis 0 with size 2"
+ if using_array_manager:
+ msg = "list index out of range"
with pytest.raises(IndexError, match=msg):
df.iat[4, 2] = 5.0