REGR: ValueError: cannot convert float NaN to integer - on dataframe.reset_index() in pandas 1.1.0 · Issue #35606 · pandas-dev/pandas (original) (raw)

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• I have confirmed this bug exists on the latest version of pandas.
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Code Sample, a copy-pastable example

from pandas.core.dtypes.cast import construct_1d_arraylike_from_scalar from pandas.core.dtypes.missing import na_value_for_dtype import numpy as np

dtype = np.datetime64().dtype length = 10 works_value = np.NaN fails_value = na_value_for_dtype(dtype)

works

construct_1d_arraylike_from_scalar(works_value, length, dtype)

fails

construct_1d_arraylike_from_scalar(fails_value, length, dtype)

Results in:

Traceback (most recent call last):
  File "<input>", line 1, in <module>
    construct_1d_arraylike_from_scalar(value, length, dtype)
  File "/usr/lib/python3.8/site-packages/pandas/core/dtypes/cast.py", line 1453, in construct_1d_arraylike_from_scalar
    subarr.fill(value)
ValueError: cannot convert float NaN to integer

Problem description

This is a problem was found when calling reset_index on a MultiIndex Dataframe with an index containing datetime information. The expected behaviour would be that it would return an array of NaTs, which ironically only happens if you pass it np.NaN.
I'm not familiar with the source code of numpy, so I can only speculate on how to fix it, but I would assume we would need special handling for time values, so we fill time arrays with np.NaNs instead of pandas._libs.tslibs.nattype.NaTTypes.

Expected Output

array(['NaT', 'NaT', 'NaT', 'NaT', 'NaT', 'NaT', 'NaT', 'NaT', 'NaT', 'NaT'], dtype=datetime64)

Output of pd.show_versions()

INSTALLED VERSIONS

commit : None
python : 3.8.3.final.0
python-bits : 64
OS : Linux
OS-release : 5.7.9-1-MANJARO
machine : x86_64
processor :
byteorder : little
LC_ALL : None
LANG : en_GB.UTF-8
LOCALE : en_GB.UTF-8

pandas : 1.0.5
numpy : 1.19.1
pytz : 2020.1
dateutil : 2.8.1
pip : 20.1.1
setuptools : 49.2.0
Cython : 0.29.21
pytest : 5.4.3
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : None
lxml.etree : 4.5.2
html5lib : 1.1
pymysql : None
psycopg2 : None
jinja2 : 2.11.2
IPython : 7.16.1
pandas_datareader: 0.10.0dev0
bs4 : 4.9.1
bottleneck : 1.3.2
fastparquet : None
gcsfs : None
lxml.etree : 4.5.2
matplotlib : 3.3.0
numexpr : 2.7.1
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pytables : None
pytest : 5.4.3
pyxlsb : None
s3fs : None
scipy : 1.5.1
sqlalchemy : 1.3.17
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
xlsxwriter : None
numba : None