ENH: Add empty property to Index. #15270

ssanderson · 2017-01-31T02:22:52Z

Previously, attempting to evaluate an Index in a boolean context prints
an error message listing various alternatives, one of which is .empty,
which was not actually implemented on Index.

closes BUG: Index doesn't have an .empty attribute #13207
tests added / passed
passes git diff upstream/master | flake8 --diff
whatsnew entry

codecov-io · 2017-01-31T02:23:03Z

Codecov Report

Merging #15270 into master will decrease coverage by -0.01%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master   #15270      +/-   ##
==========================================
- Coverage   90.37%   90.37%   -0.01%     
==========================================
  Files         135      135              
  Lines       49466    49468       +2     
==========================================
+ Hits        44705    44706       +1     
- Misses       4761     4762       +1

Impacted Files	Coverage Δ
pandas/core/base.py	`95.17% <100%> (+0.02%)`	✅
pandas/core/common.py	`91.02% <ø> (-0.34%)`	❌

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ssanderson · 2017-01-31T02:28:14Z

Happy to open a separate issue for this to close if it's desired. Whatsnew entry is currently just pointing at this PR.

jreback

pls add s whatsnew note

jreback · 2017-01-31T02:27:49Z

pandas/core/base.py

@@ -877,6 +877,10 @@ def _values(self):
        """ the internal implementation """
        return self.values

+    @property
+    def empty(self):
+        return not bool(self.size)


u can prob remove the one from series

It looks like Series is inheriting its current implementation from NDFrame, but this one will win because IndexOpsMixin appears first in its bases.

Do you think it's worth trying to push the implementation in NDFrame elsewhere?

i don't think that impl with work here but u can try

yeah, I didn't mean to imply that the NDFrame impl worked here, I meant that we could push the NDFrame impl into a subclass (e.g. into an intermediate class between NDFrame and DataFrame/Panel). I doubt that's worth the added complexity though.

jreback · 2017-01-31T02:28:07Z

pandas/tests/indexes/common.py

+
+    def test_empty(self):
+        index = self.create_index()
+        self.assertFalse(index.empty)


add this pr number as a xokment

jreback · 2017-01-31T02:30:03Z

PR number is fine

though pls search for an open issue (might be one)

ssanderson · 2017-01-31T02:43:26Z

Looks like this was actually already reported as #13207 and claims to be fixed in #13216, though that branch looks like it's had some rebasing troubles and no longer appears to have the change related to .empty.

ssanderson · 2017-01-31T02:46:24Z

Whatsnew added and comment added in the tests.

jorisvandenbossche · 2017-01-31T09:21:01Z

The other PR was linked to the wrong issue. It was indeed fixing something else (corrected that now)

jorisvandenbossche · 2017-01-31T09:23:33Z

pandas/core/base.py

@@ -877,6 +877,10 @@ def _values(self):
        """ the internal implementation """
        return self.values

+    @property
+    def empty(self):
+        return not self.values.size


Could also use self.size instead?
Index.size uses the _values instead of values. Didn't follow that recently, but I think the values get converted to objects for PeriodIndex, giving an unnecessary slowdown.

I agree this should directly use .size

jreback · 2017-01-31T14:45:15Z

@ssanderson trivial change. pls ping when green.

ssanderson · 2017-01-31T15:34:50Z

@jreback updated to just use .size.

jreback · 2017-01-31T15:37:16Z

while you are at it, can you add .empty in doc/source/api.rst (for Index, Series, DataFrame, Panel...etc)

jreback · 2017-01-31T15:38:42Z

pandas/core/base.py

@@ -877,6 +877,10 @@ def _values(self):
        """ the internal implementation """
        return self.values

+    @property
+    def empty(self):
+        return not self.size


actually this might just work for all NDFrame.

can you also move the doc-string to here.

I don't think the current docstring on NDFrame would make sense if moved here, since it makes references to NDFrame, and it has examples geared toward DataFrame, both of which would be confusing if they showed up on a property of Index.

Coming back to this with fresh eyes, I'm now inclined to just put empty on the base Index class and give it an Index-specific docstring. The root issue here is that there are two places from which Series could be getting it's implementation of empty: NDFrame, which provides shared implementations for Series/DataFrame/Panel, and IndexOpsMixin, which provides shared implementations for Index and Series. In the case of empty (and, in general, any property that belongs on both containers and indexes) I think putting the implementation on IndexOpsMixin ends up being more confusing than helpful, because it's no longer clear which implementation will end up getting used for Series. Does that seem reasonable?

Separately, I could replace the current implementation of NDFrame.empty with this if you think it's preferable, though I'm not sure it's a worthwhile improvement by itself.

you can easily fix the doc-strings by using the _shared_docs. ok with having one for Index and one in generic instead.

jreback · 2017-02-16T17:55:59Z

can you rebase / update ....so close!

Previously, attempting to evaluate an Index in a boolean context prints an error message listing various alternatives, one of which is `.empty`, which was not actually implemented on `Index`.

jreback · 2017-03-23T13:10:47Z

can you update

jreback · 2017-03-28T19:11:01Z

thanks!

Previously, attempting to evaluate an Index in a boolean context prints an error message listing various alternatives, one of which is `.empty`, which was not actually implemented on `Index`. Author: Scott Sanderson <ssanderson@quantopian.com> This patch had conflicts when merged, resolved by Committer: Jeff Reback <jeff@reback.net> closes pandas-dev#13207 Closes pandas-dev#15270 from ssanderson/add-empty-to-index and squashes the following commits: bb0126f [Scott Sanderson] ENH: Add empty property to Index.

ssanderson force-pushed the add-empty-to-index branch from 0b2826f to 3e93ff0 Compare January 31, 2017 02:27

jreback requested changes Jan 31, 2017

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ssanderson force-pushed the add-empty-to-index branch from 3e93ff0 to 66769f4 Compare January 31, 2017 02:29

ssanderson force-pushed the add-empty-to-index branch from 66769f4 to 76d6beb Compare January 31, 2017 02:45

ssanderson force-pushed the add-empty-to-index branch from 76d6beb to 9ee52a4 Compare January 31, 2017 02:58

jorisvandenbossche reviewed Jan 31, 2017

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jreback added Indexing Related to indexing on series/frames, not to indexes themselves Reshaping Concat, Merge/Join, Stack/Unstack, Explode labels Jan 31, 2017

jreback approved these changes Jan 31, 2017

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jreback added this to the 0.20.0 milestone Jan 31, 2017

ssanderson force-pushed the add-empty-to-index branch from 9ee52a4 to f329977 Compare January 31, 2017 15:34

jreback reviewed Jan 31, 2017

View reviewed changes

ENH: Add empty property to Index.

bb0126f

Previously, attempting to evaluate an Index in a boolean context prints an error message listing various alternatives, one of which is `.empty`, which was not actually implemented on `Index`.

ssanderson force-pushed the add-empty-to-index branch from f329977 to bb0126f Compare February 20, 2017 18:04

jreback removed this from the 0.20.0 milestone Mar 23, 2017

jreback added this to the 0.20.0 milestone Mar 28, 2017

jreback closed this in ec84ae3 Mar 28, 2017

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ENH: Add empty property to Index. #15270

ENH: Add empty property to Index. #15270

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ENH: Add empty property to Index. #15270

ENH: Add empty property to Index. #15270

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