Add note about limited propagation of attrs
Explicitly mention that `attrs` are not retained once a series is placed into a dataframe, related to issue #35425
@TomAugspurger  @RobertRosca is this still active? Could you address Tom's comment if so? Thanks for updating - could you also address the comment

>  for now I think adding this note to basics.rst is best.

please? Hey, sorry for the delay, forgot about the PR :sweat_smile: 

Had  a look at the `user_guide/basics.rst` page and I'm not sure where this would fit in there. There's a section ["Attributes and underlying data"](https://pandas.pydata.org/pandas-docs/stable/user_guide/basics.html#attributes-and-underlying-data) which has a reference `_basics.attrs` in the file, but that talks about metadata intrinsic to the table itself (shape, axis labels) not metadata added by users to `.attrs`. The `.attrs` dict itself doesn't seem to be mentioned on the basics page.

And since attrs is [marked as experimental](https://pandas.pydata.org/pandas-docs/stable/reference/api/pandas.Series.attrs.html), and adding your own metadata isn't really 'basic', I don't think it should be mentioned much on the page about essential basic functionality.

Personally I'd expect to find this kind of warning about the use of attrs on the doc page for  `pandas.Series.attrs`. I'm happy to put it somewhere in user_guide/basics.rst as well, but still think that a gotcha for the series attrs should be mentioned on the series attrs doc page. Hey, I added the note but to a different location to what @TomAugspurger suggested, if Tom's okay with where it is then hopefully it can be merged :smiley:  I don't think that a paragraph in the reference docs is the right place. It
should either go in the docstring or the user guide.

That said, the wording will need to be clarified. Right now it reads like
DataFrame just doesn't propagate attrs in any operation.
It shouldn't mention propagation, instead it should focus on the DataFrame
constructor not extracting attrs from individual Series.
Things like Series.to_frame() do correctly propagate attrs, so the focus
really should be on the constructor.

On Tue, Nov 3, 2020 at 2:54 AM Robert Rosca <notifications@github.com>
wrote:

> Hey, I added the note but to a different location to what @TomAugspurger
> <https://github.com/TomAugspurger> suggested, if Tom's okay with where it
> is then hopefully it can be merged 😃
>
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 Closing for now. @RobertRosca ping us know whenever you'd like to pick up and address @TomAugspurger feedback - we'll reopen