Description
Pandas version checks
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I have checked that this issue has not already been reported.
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I have confirmed this bug exists on the latest version of pandas.
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I have confirmed this bug exists on the main branch of pandas.
Reproducible Example
df = pd.DataFrame({"foo": [1, 2, 3], "bar": [4, 5, 6]})
df["foo"].iloc[0] = 100Issue Description
on main this gives
/tmp/ipykernel_19965/196554192.py:2: ChainedAssignmentError: A value is trying to be set on a copy of a DataFrame or Series through chained assignment.
When using the Copy-on-Write mode, such chained assignment never works to update the original DataFrame or Series, because the intermediate object on which we are setting values always behaves as a copy.
Try using '.loc[row_indexer, col_indexer] = value' instead, to perform the assignment in a single step.
See the caveats in the documentation: https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy
df["foo"].iloc[0] = 100
however https://pandas.pydata.org/pandas-docs/stable/user_guide/indexing.html#returning-a-view-versus-a-copy does not exist in the dev docs. (removed in #56614)
(also should the link in doc/source/whatsnew/v2.2.0.rst not fail the doc build?)
cc @phofl
Expected Behavior
probably should link to Why does assignment fail when using chained indexing? or maybe directly to https://pandas.pydata.org/docs/.../user_guide/copy_on_write.html
Installed Versions
INSTALLED VERSIONS
commit : 67055d5
python : 3.10.14.final.0
python-bits : 64
OS : Linux
OS-release : 5.4.72-microsoft-standard-WSL2
Version : #1 SMP Wed Oct 28 23:40:43 UTC 2020
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 3.0.0.dev0+272.g67055d5944
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0
setuptools : 69.5.1
pip : 24.0
Cython : 3.0.10
pytest : 8.2.0
hypothesis : 6.101.0
sphinx : 7.3.7
blosc : None
feather : None
xlsxwriter : 3.1.9
lxml.etree : 5.2.2
html5lib : 1.1
pymysql : 1.4.6
psycopg2 : 2.9.9
jinja2 : 3.1.4
IPython : 8.24.0
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : 1.3.8
fastparquet : 2024.2.0
fsspec : 2024.3.1
gcsfs : 2024.3.1
matplotlib : 3.8.4
numba : 0.59.1
numexpr : 2.9.0
odfpy : None
openpyxl : 3.1.2
pyarrow : 15.0.2
pyreadstat : 1.2.7
python-calamine : None
pyxlsb : 1.0.10
s3fs : 2024.3.1
scipy : 1.13.0
sqlalchemy : 2.0.30
tables : 3.9.2
tabulate : 0.9.0
xarray : 2024.3.0
xlrd : 2.0.1
zstandard : 0.22.0
tzdata : 2024.1
qtpy : None
pyqt5 : None