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
from pandas import NA, DataFrame, concat
a = DataFrame.from_dict({'val': [1], 'na': [NA]})
b = DataFrame.from_dict({'val': [2], 'na': [NA]})
print("a and b:")
print(a)
print(b)
print("concat:")
ab = concat([a, b])
print(ab)Issue Description
NA are coerced in to NaN by concat:
a and b:
val na
0 1 <NA>
val na
0 2 <NA>
concat:
val na
0 1 NaN
0 2 NaN
Expected Behavior
The NA stay as NA.
Installed Versions
INSTALLED VERSIONS
commit : 0691c5c
python : 3.12.2
python-bits : 64
OS : Linux
OS-release : 6.8.0-1021-azure
Version : #25~22.04.1-Ubuntu SMP Thu Jan 16 21:37:09 UTC 2025
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : C.UTF-8
pandas : 2.2.3
numpy : 1.26.4
pytz : 2025.2
dateutil : 2.9.0.post0
pip : 24.0
Cython : None
sphinx : None
IPython : None
adbc-driver-postgresql: None
adbc-driver-sqlite : None
bs4 : None
blosc : None
bottleneck : None
dataframe-api-compat : None
fastparquet : None
fsspec : None
html5lib : None
hypothesis : None
gcsfs : None
jinja2 : 3.1.6
lxml.etree : 5.2.2
matplotlib : None
numba : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
psycopg2 : None
pymysql : None
pyarrow : 17.0.0
pyreadstat : None
pytest : None
python-calamine : None
pyxlsb : None
s3fs : None
scipy : 1.11.2
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlsxwriter : None
zstandard : None
tzdata : 2025.2
qtpy : None
pyqt5 : None