BUG: join resets index even when doing left join on empty dataframes · Issue #52777 · pandas-dev/pandas (original) (raw)

Pandas version checks

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• I have confirmed this bug exists on the latest version of pandas.
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Reproducible Example

import pandas as pd

foo = pd.DataFrame([], index=pd.Index([], dtype="object")) bar = foo.copy()

foo.join(bar).indexfoo.join(bar).index

Issue Description

On Pandas 1.5.3 above example produces Index([], dtype='object') while on 2.0.0 it produces RangeIndex(start=0, stop=0, step=1). I have not found this change in the release notes so I have to assume it is an unintended change and it causes unwanted consequences.

Expected Behavior

I expect the same behavior as in version 1.5.3

Installed Versions

INSTALLED VERSIONS

commit : 2e218d1
python : 3.10.6.final.0
python-bits : 64
OS : Linux
OS-release : 5.19.0-38-generic
Version : #39~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Fri Mar 17 21:16:15 UTC 2
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.5.3
numpy : 1.24.1
pytz : 2022.6
dateutil : 2.8.2
setuptools : 59.6.0
pip : 23.0
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.7.0
pandas_datareader: None
bs4 : 4.11.1
bottleneck : None
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.6.3
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None
tzdata : 2023.3