Add tests to ensure sort preserved by groupby, add docs #10931
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nickeubank force-pushed the test_groupby_sort_preservation branch 5 times, most recently from ed6eb1a to 8bcd4a5 Compare 
doc/source/groupby.rst Outdated
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hmm, this is True, but I think the average user will find this a bit confusing. Can you expand/reword a bit. (its an important point), but not sure how to describe it.
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Ok -- dropped the discussion of what exactly is happening behind the scenes, tried to clear up the explanation above, and fleshed out the examples a little more. That clearer?
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Is there any reason a user would even expect that the already created groupby object would change after sorting the original frame?
Is there an example of confusion? As adding this explanation of something that I would have never thought of seems to make it only more complex than it should be IMO
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I agree with Joris. This behavior is entirely consistent with the standard memory model in Python. It does not need explaining.
nickeubank force-pushed the test_groupby_sort_preservation branch 2 times, most recently from c77e701 to f579d6e Compare 
| @jreback updated! |
doc/source/groupby.rst Outdated
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Can you hard wrap here?
| The basic part on sort=True/False and sort preserved within groups looks good! However, I don't really seem to grasp the need to explain the sorting after groupby: "Users should be careful about re-sorting their data after execution of |
nickeubank force-pushed the test_groupby_sort_preservation branch 2 times, most recently from b060c0e to 4817cb3 Compare | @jorisvandenbossche @shoyer @jreback OK, warning dropped! |
pandas/core/generic.py Outdated
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sorted order -> order ? (as the order within a group is not necessarily sorted?)
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what about "order in which observations appear"?
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or just order of observations?
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or 'rows'?
groupby preserves the order of the rows within each group
nickeubank force-pushed the test_groupby_sort_preservation branch from 4817cb3 to 3b49fad Compare | @jorisvandenbossche great, added. |
Add tests to ensure sort preserved by groupby, add docs
| @nickeubank thanks! |
4 participants
xref #9651
closes #8588
Adds test to ensure the sort of a target object is preserved within
groupby()groups, modifies docs to make it clear sort is preserved within groups.