BUG: Setting values on DataFrame with multi-index .loc(axis=0) access adds columns · Issue #58116 · pandas-dev/pandas (original) (raw)

Pandas version checks

Reproducible Example

import pandas as pd

dates = pd.date_range("2001-01-01", freq="D", periods=2) ids = ["i1", "i2"] index = pd.MultiIndex.from_product([dates, ids], names=["date", "identifier"]) frame = pd.DataFrame(0.0, index=index, columns=["A", "B"]) frame.loc(axis=0)["2001-01-01", ["i1", "i2"]] = None frame

                    A    B i1 i2

date identifier
2001-01-01 i1 NaN NaN None None i2 NaN NaN None None 2001-01-02 i1 0.0 0.0 NaN NaN i2 0.0 0.0 NaN NaN

Issue Description

Setting a multi-indexed DataFrame adds columns.

Expected Behavior

No columns added, i.e. behaviour as outlined in https://pandas.pydata.org/docs/user_guide/advanced.html#advanced-indexing-with-hierarchical-index.

Installed Versions

NSTALLED VERSIONS

commit : bdc79c1
python : 3.10.14.final.0
python-bits : 64
OS : Darwin
OS-release : 23.4.0
Version : Darwin Kernel Version 23.4.0: Wed Feb 21 21:44:43 PST 2024; root:xnu-10063.101.15~2/RELEASE_ARM64_T6000
machine : arm64
processor : arm
byteorder : little
LC_ALL : None
LANG : None
LOCALE : None.UTF-8

pandas : 2.2.1
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0
setuptools : 69.2.0
pip : 24.0
Cython : None
pytest : 7.4.4
hypothesis : None
sphinx : 6.2.1
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.3
IPython : 8.22.2
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.7.3
numba : 0.59.0
numexpr : 2.9.0
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 14.0.2
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.12.0
sqlalchemy : None
tables : 3.9.2
tabulate : 0.9.0
xarray : None
xlrd : None
zstandard : None
tzdata : 2024.1
qtpy : None
pyqt5 : None