Description
Pandas version checks
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I have checked that this issue has not already been reported.
-
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
See below.Issue Description
Reproducible example
import pandas as pd
data = {
"Column2": [10, 20, 30],
"Column3": ["A", "B", "C"],
"Column4": ["Lala", "YesYes", "NoNo"],
}
df1 = pd.DataFrame(data)import polars as pl
data = {
"Column1": ["Text1", "Text2", "Text3"],
"Column2": [10, 20, 30],
"Column3": ["A", "B", "C"]
}
df2 = pl.DataFrame(data)result = df1.join(df2, on=["Column2", "Column3"], how="inner")Log output
---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
~\AppData\Local\Temp\ipykernel_11612\367032622.py in ?()
----> 1 result = df1.join(df2, on=["Column2", "Column3"], how="inner")
c:\Users\name\AppData\Local\Programs\Python\Python312\Lib\site-packages\pandas\core\frame.py in ?(self, other, on, how, lsuffix, rsuffix, sort, validate)
10766 validate=validate,
10767 )
10768 else:
10769 if on is not None:
> 10770 raise ValueError(
10771 "Joining multiple DataFrames only supported for joining on index"
10772 )
10773
ValueError: Joining multiple DataFrames only supported for joining on indexExpected Behavior
Expected Result
Error message is not correct.
It should say that joining pandas dataframe with polars dataframe is not supported.
This is how Polars formulates the error when joining the other way around:
TypeError: expected other join table to be a DataFrame, not 'pandas.core.frame.DataFrame'
Installed Versions
INSTALLED VERSIONS
commit : 0691c5c
python : 3.12.9
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19045
machine : AMD64
processor : Intel64 Family 6 Model 140 Stepping 1, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : Dutch_Netherlands.1252
pandas : 2.2.3
numpy : 2.2.5
pytz : 2025.2
dateutil : 2.9.0.post0
pip : 25.1.1
Cython : None
sphinx : None
IPython : 9.2.0
adbc-driver-postgresql: None
...
zstandard : None
tzdata : 2025.2
qtpy : None
pyqt5 : None