BUG: Check for duplicate names columns and index in crosstab

[cuchoi]

• closes Crosstab Not Working with Duplicate Column Labels #22529
• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[WillAyd]

Can you add tests? Ideally the first part of any PR

[cuchoi]

Sure! Wanted to know that this was the right approach to solving this issue before writing the tests (sorry, first PR to pandas!)

[pep8speaks]

Hello @cuchoi! Thanks for updating this PR. We checked the lines you've touched for PEP 8 issues, and found:

There are currently no PEP 8 issues detected in this Pull Request. Cheers! 🍻

Comment last updated at 2019-06-09 22:09:06 UTC

[cuchoi]

Added tests. Basically updated an old test that would break if we used different data. This would break before:

""" We create two series, rename one of the columns, 
    do a crosstab and check if they are equal. We expect them to be equal,
    but it fails due to an issue when there are duplicate column names."""
s1 = pd.Series(range(3), name='foo')
s2 = s1 + 1

expected = pd.crosstab(s1, s2.rename("bar"))
result = pd.crosstab(s1, s2)

tm.assert_frame_equal(result, expected)

So now I add raises exceptions checking in case that there is:

• A duplicated index
• Duplicated columns
• Name shared between the index and columns.

[codecov]

Codecov Report

❗ No coverage uploaded for pull request base (master@9a67ff4). Click here to learn what that means.
The diff coverage is 0%.

@@            Coverage Diff            @@
##             master   #26717   +/-   ##
=========================================
  Coverage          ?   41.19%           
=========================================
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  Branches          ?        0           
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  Hits              ?    20918           
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Flag	Coverage Δ
#single	41.19% <0%> (?)

Impacted Files	Coverage Δ
pandas/core/reshape/pivot.py	8.02% <0%> (ø)

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[codecov]

Codecov Report

Merging #26717 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #26717      +/-   ##
==========================================
- Coverage   91.71%    91.7%   -0.01%     
==========================================
  Files         178      178              
  Lines       50740    50747       +7     
==========================================
+ Hits        46538    46540       +2     
- Misses       4202     4207       +5

Flag	Coverage Δ
#multiple	90.3% <100%> (ø)	⬆️
#single	41.2% <0%> (-0.12%)	⬇️

Impacted Files	Coverage Δ
pandas/core/reshape/pivot.py	96.6% <100%> (+0.07%)	⬆️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/frame.py	96.88% <0%> (-0.12%)	⬇️
pandas/util/testing.py	90.84% <0%> (-0.11%)	⬇️

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[jreback]

can you merge master and see if you can get this passing

[jbrockmendel]

@cuchoi pls rebase

[WillAyd]

Looks like this has gone stale but ping if you'd like to pick it back up

[cuchoi]

Hi! I rebased. Is it not showing up because the issue is closed? Can your reopen it?

[TomAugspurger]

Yes. GitHub struggles with reopening PRs to branches that have been closed. You're probably best off opening a new PR if you're wanting to work on this again!

[cuchoi]

Thanks! New PR here: #28474