Description
import pandas as pd
import numpy as np
frame = pd.DataFrame(index=pd.Index([1, np.nan]))
fixed_index = frame.index.where(frame.index.notna(), 'a' + frame.reset_index().index.astype(str))
Traceback (most recent call last):
File "<input>", line 4, in <module>
File "C:\Users\Miniconda3\envs\testbed_dtype\lib\site-packages\pandas\core\indexes\base.py", line 3791, in where
return self._shallow_copy_with_infer(values, dtype=dtype)
File "C:\Users\Miniconda3\envs\testbed_dtype\lib\site-packages\pandas\core\indexes\base.py", line 567, in _shallow_copy_with_infer
return Index(values, **attributes)
File "C:\Users\Miniconda3\envs\testbed_dtype\lib\site-packages\pandas\core\indexes\base.py", line 385, in __new__
data = _maybe_cast_with_dtype(data, dtype, copy)
File "C:\Users\Miniconda3\envs\testbed_dtype\lib\site-packages\pandas\core\indexes\base.py", line 5457, in _maybe_cast_with_dtype
data = data.astype(dtype)
ValueError: could not convert string to float: 'a1'Problem description
Data is being cast to incorrect dtype based on inferred dtype and gives a ValueError.
Issue was not present in pandas==0.25.3
Expected Output
With pandas==0.25.3
fixed_index
Index([1.0, 'a1'], dtype='object')
Output of pd.show_versions()
python : 3.7.6.final.0
pandas : 1.0.1
numpy : 1.18.1
pytz : 2019.3
dateutil : 2.8.1
pip : 20.0.2
setuptools : 45.2.0.post20200210
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 : None
fastparquet : None
gcsfs : None
lxml.etree : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : 3.0.3
pandas_gbq : None
pyarrow : None
pytables : None
pytest : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : 1.3.0
xlsxwriter : None
numba : None