BUG: dataframe.to_csv calls defauly numpy to_string function, resulting in

[mtscott321]

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
import numpy as np

array = np.ones((1000, 1000))
df = pd.DataFrame({"Data": [array]})
df.to_csv('test.csv', index=False)

Issue Description

The output file will then have the following in the cell:

array([[1., 1., 1., ..., 1., 1., 1.],
[1., 1., 1., ..., 1., 1., 1.],
[1., 1., 1., ..., 1., 1., 1.],
...,
[1., 1., 1., ..., 1., 1., 1.],
[1., 1., 1., ..., 1., 1., 1.],
[1., 1., 1., ..., 1., 1., 1.]])

Expected Behavior

I would expect the code to run like the following code does:

import pandas as pd
import numpy as np

array = np.ones((1000, 1000))
df = pd.DataFrame({"Data": [array]})
with np.printoptions(linewidth=1000000, threshold=np.inf):
df.to_csv('corrected_test.csv', index=False)

Where the df.to_csv function does not call the default numpy print statement.

Installed Versions

INSTALLED VERSIONS

commit : d9cdd2e
python : 3.9.20.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.26100
machine : AMD64
processor : Intel64 Family 6 Model 165 Stepping 5, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_United States.1252

pandas : 2.2.2
numpy : 1.26.4
pytz : 2024.1
dateutil : 2.9.0.post0
setuptools : 75.1.0
pip : 24.2
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.4
IPython : 8.15.0
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.3
bottleneck : 1.4.2
dataframe-api-compat : None
fastparquet : None
fsspec : None
gcsfs : None
matplotlib : 3.9.2
numba : None
numexpr : 2.10.1
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.13.1
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : 2.4.1
pyqt5 : None

[rhshadrach]

Thanks for the report. I think you're asking for pandas to change the __str__ behavior of a Python object. I'm negative on this, it is up to the user to control.

[Jahanvi-vy]

take

[mroeschke]

Agreed, especially since repr/IO writer support for nested values is not well supported generally and discouraged. Closing