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
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randint(0, 100, size=(5, 2)), columns=list('AB'))
# Assigning string directly works
df.loc[df.index < 2, 'E'] = 'abc'
# Assigning a string and a float in the same step raises a Future warning
df.loc[df.index <= 2, ['F', 'G']] = (1, 'abc', )
# DOing the same assignment unconditionally does NOT raise the future warning
df.loc[:, ['I', 'J']] = (1, 'abc', )
df.head()
Issue Description
String assignment future warnings are quite flaky and seem to change and break in different ways in every recent version.
While most issues i've seen have been fixed - i just encountered a new issue, where behavior is completely non-uniform and surprising
I can reproduce this in anything after 2.1.x - including 2.1.4 - which is the latest current release
2.0.3 doesn't issue this - but i think these flaky FutureWarnings were only introduced in 2.0.3.
Expected Behavior
No future warning when creating a new string column - independant of the precence of another column in the assignment (and independent of a filter).
Installed Versions
INSTALLED VERSIONS
commit : a671b5a
python : 3.11.4.final.0
python-bits : 64
OS : Linux
OS-release : 6.6.3-arch1-1
Version : #1 SMP PREEMPT_DYNAMIC Wed, 29 Nov 2023 00:37:40 +0000
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8
pandas : 2.1.4
numpy : 1.26.2
pytz : 2023.3
dateutil : 2.8.2
setuptools : 68.2.2
pip : 23.3.1
Cython : 0.29.35
pytest : 7.4.3
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.9.3
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.14.0
pandas_datareader : None
bs4 : 4.12.2
bottleneck : None
dataframe-api-compat: None
fastparquet : None
fsspec : 2023.12.1
gcsfs : None
matplotlib : 3.7.1
numba : None
numexpr : 2.8.4
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 14.0.1
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : 1.11.4
sqlalchemy : 2.0.23
tables : 3.9.1
tabulate : 0.9.0
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None