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Behavior change in Index.equals from 0.18.0 to 0.19.0 -- intentional? #14411

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njsmith opened this issue Oct 13, 2016 · 2 comments · Fixed by #27105
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Behavior change in Index.equals from 0.18.0 to 0.19.0 -- intentional? #14411

njsmith opened this issue Oct 13, 2016 · 2 comments · Fixed by #27105
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Docs Index Related to the Index class or subclasses
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0.25.0

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@njsmith
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njsmith commented Oct 13, 2016

Traditionally, we have:

In [3]: pandas.__version__
Out[3]: '0.18.0'

In [4]: pandas.Index([1, 2]).equals([1, 2])
Out[4]: True

But this changed

In [4]: pandas.__version__
Out[4]: '0.19.0'

In [5]: pandas.Index([1, 2]).equals([1, 2])
Out[5]: False

Looks like it might not be intentional so FYI.

(Noticed because it broke a few tests in the patsy test suite.)
njsmith added a commit to njsmith/patsy that referenced this issue Oct 13, 2016
@njsmith
Work around pandas.Index.equals change in 0.19.0
a83ff74 
Traditionally, `pandas.Index([1, 2]).equals([1, 2])` returned True. In
0.19.0, it returns False, and we have to explicitly upcast the argument
to an Index to get the test we want.

pandas-dev/pandas#14411
@jorisvandenbossche
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jorisvandenbossche commented Oct 13, 2016 •
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Well, we had some discussion about this, see #13986 (comment) (I thought we had a longer discussion somewhere else, but can't find it directly), but I think I lost the discussion for allowing this.
Basically, to be equal to an index, you now have to be an index yourself (so a list can no longer be equal). But I see we didn't really explain this in the whatsnew docs.

@jorisvandenbossche jorisvandenbossche added the Indexing Related to indexing on series/frames, not to indexes themselves label Oct 13, 2016
@njsmith
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njsmith commented Oct 13, 2016

I can see the argument for the new behavior, but it was a backwards incompatible change with no deprecation, so wasn't sure what was going on.

I've already worked around it for patsy.

@toobaz toobaz added Index Related to the Index class or subclasses Docs and removed Indexing Related to indexing on series/frames, not to indexes themselves labels Jun 28, 2019
toobaz added a commit to toobaz/pandas that referenced this issue Jun 28, 2019
@toobaz
DOC: clarify that Index.equals(non_index) returns False
0134de6 
closes pandas-dev#14411
@toobaz toobaz mentioned this issue Jun 28, 2019
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@jreback jreback added this to the 0.25.0 milestone Jun 28, 2019
jorisvandenbossche pushed a commit that referenced this issue Jun 28, 2019
@toobaz @jorisvandenbossche
DOC: clarify that Index.equals(non_index) returns False (#27105)
9693230 
closes #14411
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DOC: clarify that Index.equals(non_index) returns False toobaz/pandas
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