BUG: Pandas converts nullable int to float, even when this loses data #63903
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
def add_two(x):
if pd.isna(x):
return pd.NA
return x+2
sequence = [10000000000000001,None] #above the float integer precision limit
df1 = pd.DataFrame(sequence, dtype='Int64')
df1[0] = df1[0].apply(add_two).astype('Int64')
print(int(df1[0][0])) # 002, not 003Issue Description
Anytime there's a null value in a series when using .apply() (or creating a dataframe with no dtype specified), it will be converted to a float, even if the data type it already is can support null values, and is a better fit for the data, and this results in loss of precision compared to not converting
Possibly related to #62710
Expected Behavior
Pandas should not convert data types to a float when this loses data and is a worse fit for the data.
Installed Versions
Details
INSTALLED VERSIONS
commit : 366ccdf
python : 3.14.2
python-bits : 64
OS : Windows
OS-release : 11
Version : 10.0.26200
machine : AMD64
processor : Intel64 Family 6 Model 165 Stepping 2, GenuineIntel
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : English_Canada.1252
pandas : 3.0.0
numpy : 2.4.1
dateutil : 2.9.0.post0
pip : 25.3
Cython : None
sphinx : None
IPython : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
bottleneck : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : None
lxml.etree : None
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
psycopg2 : None
pymysql : None
pyarrow : None
pyiceberg : None
pyreadstat : None
pytest : None
python-calamine : None
pytz : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
qtpy : None
pyqt5 : None