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BUG: read_csv loses precision when engine='pyarrow' and dtype Int64 #56136

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MarcoGorelli opened this issue Nov 23, 2023 · 2 comments
Open
3 tasks done
Labels
Arrow pyarrow functionality Bug IO CSV read_csv, to_csv NA - MaskedArrays Related to pd.NA and nullable extension arrays

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@MarcoGorelli
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Pandas version checks

  • I have checked that this issue has not already been reported.

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

  • I have confirmed this bug exists on the main branch of pandas.

Reproducible Example

data = """a,b
1,1
,1
1582218195625938945,1
"""
result = pd.read_csv(StringIO(data), dtype={"a": "Int64"}, engine='pyarrow')

Issue Description

this outputs

In [69]: result
Out[69]:
                     a  b
0                    1  1
1                 <NA>  1
2  1582218195625938944  1

Expected Behavior

In [69]: result
Out[69]:
                     a  b
0                    1  1
1                 <NA>  1
2  1582218195625938945  1

Installed Versions

INSTALLED VERSIONS

commit : 1c606d5
python : 3.10.12.final.0
python-bits : 64
OS : Linux
OS-release : 5.10.102.1-microsoft-standard-WSL2
Version : #1 SMP Wed Mar 2 00:30:59 UTC 2022
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8

pandas : 2.2.0.dev0+694.g1c606d5f01
numpy : 1.25.1
pytz : 2023.3
dateutil : 2.8.2
setuptools : 67.6.1
pip : 23.1.2
Cython : None
pytest : 7.3.1
hypothesis : 6.82.4
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : 3.1.2
IPython : 8.16.1
pandas_datareader : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : 4.12.2
bottleneck : None
dataframe-api-compat : None
fastparquet : 2023.7.0
fsspec : 2023.6.0
gcsfs : None
matplotlib : 3.7.1
numba : 0.58.1
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 12.0.1
pyreadstat : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.11.0
sqlalchemy : 2.0.20
tables : None
tabulate : None
xarray : None
xlrd : None
zstandard : None
tzdata : 2023.3
qtpy : None
pyqt5 : None

@MarcoGorelli MarcoGorelli added Bug Needs Triage Issue that has not been reviewed by a pandas team member Arrow pyarrow functionality IO CSV read_csv, to_csv and removed Needs Triage Issue that has not been reviewed by a pandas team member labels Nov 23, 2023
@MarcoGorelli
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This was hiding due to #55882

cc @phofl

@phofl
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phofl commented Nov 23, 2023

Yeah this is round tripping through float and a know issue

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Labels
Arrow pyarrow functionality Bug IO CSV read_csv, to_csv NA - MaskedArrays Related to pd.NA and nullable extension arrays
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