Description
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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 master branch of pandas.
Reproducible Example
import pandas as pd
df = pd.DataFrame(columns = ["A", "B"])
col = df.columns.insert(-1, "C")
print(col)
df = pd.DataFrame( columns = col)
print(df.columns)Issue Description
the method index.insert does not allow to insert a value last.
loc=-1 gives an insertion at the second last place
'loc=0=-0' gives an insertion at 1st place
Expected Behavior
The method index.insert should follow the standard loc function and 'loc=-1' should insert the item last in the index
Installed Versions
INSTALLED VERSIONS
commit : 945c9ed
python : 3.8.10.final.0
python-bits : 64
OS : Linux
OS-release : 5.4.129+
Version : #1 SMP Wed Aug 18 19:58:18 PDT 2021
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : None
LOCALE : en_US.UTF-8
pandas : 1.3.4
numpy : 1.21.3
pytz : 2021.3
dateutil : 2.8.2
pip : 20.0.2
setuptools : 45.2.0
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
fsspec : None
fastparquet : None
gcsfs : None
matplotlib : None
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : None
pyxlsb : None
s3fs : None
scipy : None
sqlalchemy : None
tables : None
tabulate : None
xarray : None
xlrd : None
xlwt : None
numba : None
None