BUG: when re-index is filling values for both index and columns with dtype uint8 the filled values are incorrect · Issue #48184 · pandas-dev/pandas (original) (raw)

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

import pandas as pd

this example works correctly, showing that the bug is not on all dtypes

df = pd.DataFrame([[1,2], [3, 4]], index=list('ab'), columns=list('qw'), dtype='int64') df.reindex(index=list('abcd'), columns=list('qwer'), fill_value=10)

this example has the bug

df = pd.DataFrame([[1,2], [3, 4]], index=list('ab'), columns=list('qw'), dtype='uint8') df.reindex(index=list('abcd'), columns=list('qwer'), fill_value=10)

this example works correctly, showing that it is only a bug when both index and columns are specified

df = pd.DataFrame([[1,2], [3, 4]], index=list('ab'), columns=list('qw'), dtype='uint8') df.reindex(index=list('abcd'), fill_value=10).reindex(columns=list('qwer'), fill_value=10)

Issue Description

When using the fill_value option in the reindex method, when both index and columns are specified and the dtype is uint8 (note I did not try to find all dtypes that have this error), the NaNs are not being replaced by the fill_value, instead they are broadcasting the last item in the dataframe.

Default case that works as expected when using dtype='int64'

The bug when using dtype='uint8' and how the bug goes away when not passing in the index and columns at the same time.

Expected Behavior

df = pd.DataFrame([[1,2], [3, 4]], index=list('ab'), columns=list('qw'), dtype='uint8')
df_new = df.reindex(index=list('abcd'), fill_value=10).reindex(columns=list('qwer'), fill_value=10)

df_expected = pd.DataFrame([[1,2, 10, 10], [3, 4, 10, 10], [10, 10, 10, 10], [10, 10, 10, 10]], index=list('abcd'), columns=list('qwer'), dtype='uint8')
assert df_new.equals(df_expected)

Installed Versions

INSTALLED VERSIONS

commit : e8093ba
python : 3.9.12.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19044
machine : AMD64
processor : Intel64 Family 6 Model 78 Stepping 3, GenuineIntel
byteorder : little
LC_ALL : None
LANG : None
LOCALE : English_Canada.1252
pandas : 1.4.3
numpy : 1.23.1
pytz : 2022.1
dateutil : 2.8.2
setuptools : 61.2.0
pip : 22.1.2
Cython : None
pytest : None
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : None
html5lib : None
pymysql : None
psycopg2 : None
jinja2 : None
IPython : None
pandas_datareader: None
bs4 : None
bottleneck : 1.3.5
brotli : None
fastparquet : None
fsspec : None
gcsfs : None
markupsafe : None
matplotlib : None
numba : None
numexpr : 2.8.3
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyreadstat : None
pyxlsb : None
s3fs : None
scipy : None
snappy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
zstandard : None