TST: add test cases for reset_index method

[minggli]

• closes BUG: reset_index can reset index name #17067
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

the fix appears to work but it breaks previous assert_frame_equal that assumes index.name == None after reset_index() call.

The question remains that is the issue #17067 actually a bug and does it require a fix at all? user can pretty much do series.index.name = 'new name' to handle this problem.

[pep8speaks]

Hello @minggli! Thanks for submitting the PR.

• There are no PEP8 issues in the file pandas/core/frame.py !

• There are no PEP8 issues in the file pandas/core/indexes/base.py !

• There are no PEP8 issues in the file pandas/core/series.py !

[jreback]

there are 2 issues pointed out in the OP

the first should already be fixed (and was a bug)

to answer your question, yes we want to be consistent in this

[minggli]

@jreback thanks for commenting! it seems it has indeed been fixed already. closing this PR.

[jreback]

would take tests for this though!

[minggli]

strangely, it appears that below would fail on master:

s = pd.Series([1, 2, 3], index=pd.Index(range(3), name='x'))
assert s.reset_index().index.name == 'x'
assert s.reset_index(drop=True).index.name == 'x'

i hope I understood the issue correctly, is it expected for the reset index to carry over the index name?

[jreback]

In [11]: s.reset_index(drop=True).index.name == 'x'
Out[11]: False

In [12]: s.reset_index().index.name == 'x'
Out[12]: False

these both look correct to me, the index name should not be carried over.

[codecov]

Codecov Report

Merging #23116 into master will increase coverage by 0.62%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #23116      +/-   ##
==========================================
+ Coverage   92.19%   92.82%   +0.62%     
==========================================
  Files         169      169              
  Lines       50950    55686    +4736     
==========================================
+ Hits        46975    51689    +4714     
- Misses       3975     3997      +22

Flag	Coverage Δ
#multiple	91.37% <ø> (+0.75%)	⬆️
#single	43.7% <ø> (+1.43%)	⬆️

Impacted Files	Coverage Δ
pandas/io/common.py	68.62% <0%> (-2.42%)	⬇️
pandas/core/arrays/period.py	95.47% <0%> (-0.1%)	⬇️
pandas/util/testing.py	86.5% <0%> (+0.05%)	⬆️
pandas/core/indexes/datetimelike.py	98.37% <0%> (+0.12%)	⬆️
pandas/io/formats/csvs.py	98.39% <0%> (+0.17%)	⬆️
pandas/core/arrays/categorical.py	95.74% <0%> (+0.2%)	⬆️
pandas/core/arrays/sparse.py	92.76% <0%> (+0.24%)	⬆️
pandas/core/arrays/datetimelike.py	95.57% <0%> (+0.67%)	⬆️
pandas/core/arrays/datetimes.py	98.05% <0%> (+0.67%)	⬆️
pandas/core/frame.py	97.84% <0%> (+0.72%)	⬆️
... and 12 more

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[minggli]

@jreback reflected your comment in added tests.

[jreback]

thanks @minggli

[minggli]

welcome! @jreback @gfyoung 😃