Description
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Note: Please read this guide detailing how to provide the necessary information for us to reproduce your bug.
Code Sample, a copy-pastable example
print(
pd.Series(dtype="bool").reindex([0]),
"\n\n",
pd.Series(index=[0], dtype="bool"),
"\n\n",
pd.Series(dtype="bool").reindex([0]).astype(bool),
)Problem description
This is the output:
0 NaN
dtype: object
0 False
dtype: bool
0 True
dtype: bool
Semantically we may expect the same behavior for the code above. The second and third cases are definitely contradictory and dangerous.
I use the following code to test some common types, and it fails for type bool (another case that would fail is int, which I reported in #43017)
for dtype in [bool, "Int64", "float", "datetime64[ns]", "timedelta64[ns]"]:
print("***", dtype, "***")
s1 = pd.Series(dtype=dtype).reindex([0])
s2 = pd.Series(index=[0], dtype=dtype)
s3 = pd.Series(dtype=dtype).reindex([0]).astype(dtype)
print(s1.equals(s2), s1.equals(s3))Expected Output
Either
0 NaN
dtype: object
or
0 False
dtype: bool
makes sense. However, we get True when testing bool(np.nan), which explains some of the inconsistent behavior above.
Output of pd.show_versions()
INSTALLED VERSIONS
commit : c7f7443
python : 3.7.11.final.0
python-bits : 64
OS : Windows
OS-release : 10
Version : 10.0.19041
machine : AMD64
processor : Intel64 Family 6 Model 142 Stepping 10, GenuineIntel
byteorder : little
LC_ALL : None
LANG : en_US.UTF-8
LOCALE : None.None
pandas : 1.3.1
numpy : 1.20.3
pytz : 2021.1
dateutil : 2.8.2
pip : 21.2.2
setuptools : 52.0.0.post20210125
Cython : 0.29.24
pytest : 6.1.2
hypothesis : 6.14.1
sphinx : 4.0.2
blosc : None
feather : None
xlsxwriter : 1.4.4
lxml.etree : 4.6.3
html5lib : 1.1
pymysql : 1.0.2
psycopg2 : None
jinja2 : 3.0.1
IPython : 7.22.0
pandas_datareader: None
bs4 : 4.9.3
bottleneck : 1.3.2
fsspec : 2021.07.0
fastparquet : None
gcsfs : None
matplotlib : 3.4.2
numexpr : 2.7.3
odfpy : None
openpyxl : 3.0.7
pandas_gbq : None
pyarrow : 3.0.0
pyxlsb : None
s3fs : 0.4.2
scipy : 1.6.2
sqlalchemy : 1.4.22
tables : 3.6.1
tabulate : 0.8.9
xarray : 0.19.0
xlrd : 2.0.1
xlwt : 1.3.0
numba : 0.53.0