DOC: Mention Index.equals takes into account order of arguments

[jlandercy]

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Code Sample, a copy-pastable example

import pandas as pd
pd.Index(['10607', '6574', '6621', '99917']).equals(pd.Index(['99917', '10607', '6574', '6621'])) # False
set(['10607', '6574', '6621', '99917']) == set(['99917', '10607', '6574', '6621']) # True

Problem description

I have seen #13708, but according to documentation:

Determine if two Index objects contain the same elements.

Should it return True instead?

Reading how the function is implemented:

pandas/pandas/core/indexes/base.py

Lines 4072 to 4074 in 3adf334

	return array_equivalent(
	com.values_from_object(self), com.values_from_object(other)
	)

It relies on:

pandas/pandas/core/dtypes/missing.py

Lines 421 to 431 in 3adf334

	Examples
	--------
	>>> array_equivalent(
	... np.array([1, 2, np.nan]),
	... np.array([1, 2, np.nan]))
	True
	>>> array_equivalent(
	... np.array([1, np.nan, 2]),
	... np.array([1, 2, np.nan]))
	False
	"""

Which is indeed strict and do take order into account.

Expected Output

As I understand the equality of index is about having the same elements. It is not required the elements having the same order. I have the feeling that once pandas worked this way (maybe before v0.23).

What is the intended way ? Maybe the documentation should be a bit more explicit about this comparison. If you indicate me where I can update the doc, I will be glad to edit it.

Output of pd.show_versions()

commit : None
python : 3.6.9.final.0
python-bits : 64
OS : Linux
OS-release : 4.15.0-91-generic
machine : x86_64
processor : x86_64
byteorder : little
LC_ALL : None
LANG : C.UTF-8
LOCALE : en_US.UTF-8

pandas : 1.0.3
numpy : 1.18.2
pytz : 2019.3
dateutil : 2.8.1
pip : 9.0.1
setuptools : 46.1.3
Cython : 0.29.14
pytest : 5.3.2
hypothesis : None
sphinx : None
blosc : None
feather : None
xlsxwriter : 1.1.8
lxml.etree : 4.3.4
html5lib : 0.999999999
pymysql : None
psycopg2 : 2.8.4 (dt dec pq3 ext lo64)
jinja2 : 2.11.1
IPython : 7.13.0
pandas_datareader: None
bs4 : 4.7.1
bottleneck : None
fastparquet : None
gcsfs : None
lxml.etree : 4.3.4
matplotlib : 3.2.1
numexpr : None
odfpy : None
openpyxl : None
pandas_gbq : None
pyarrow : 0.13.0
pytables : None
pytest : 5.3.2
pyxlsb : None
s3fs : None
scipy : 1.4.1
sqlalchemy : 1.3.15
tables : None
tabulate : 0.8.3
xarray : None
xlrd : 1.2.0
xlwt : 1.3.0
xlsxwriter : 1.1.8
numba : None

[dsaxton]

I think that like the other issue this is really a problem with the documentation and not an actual bug (the method tests for equivalence and not just having the same elements as you point out). I would think that a PR to fix the documentation makes sense?

[mroeschke]

Agreed. The documentation can be clarified to mention that order is significant.

[ShaharNaveh]

take