DataFrame.groupby doesn't preserve _metadata

[pandichef]

I'm following the 0.25.3 documentation on using _metadata.

sdf = SubclassedDataFrame2(my_data_as_dictionary)
sdf.added_property = 'hello pandas'
df = sdf.groupby('mycategorical')[['myfloat1', 'myfloat2']].sum()
print(df.added_property)

The above output produces the result:
AttributeError: 'DataFrame' object has no attribute 'added_property'

added_property is not being "passed to manipulation results" as described in the documentation.

[TomAugspurger]

FYI, this is likely fixed as part of #28394, where I'm calling __finalize__ in more places.

[pandichef]

Ok. I'll check it out. Are you saying that SubclassedDataFrame.groupby.sum would now return a SubclassedDataFrame instead of a regular DataFrame? That's the only way I could the metadata being preserved. ᐧ

…

On Wed, Nov 6, 2019 at 4:09 PM Tom Augspurger ***@***.***> wrote: FYI, this is likely fixed as part of #28394 <#28394>, where I'm calling __finalize__ in more places. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#29442?email_source=notifications&email_token=AEHNEILZT66OEBW7HZR5UJLQSMXB5A5CNFSM4JJ4VGDKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEDH7V6Q#issuecomment-550501114>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEHNEIIS3RXSKZQ3KDRSP3LQSMXB5ANCNFSM4JJ4VGDA> .

[pandichef]

Fyi, this is still an issue on pandas 1.0.3. @TomAugspurger I think there is a relatively quick fix that I'm using in a personal project... in DataFrameGroupBy, you have access to self.obj. So you can write a class decorator to implement the following logic at the end of every method in DataFrameGroupBy:

if isinstance(method_result, DataFrame) and issubclass(self.obj.__class__, DataFrame):
    return self.obj.__class__(result)
elif isinstance(method_result, Series) and issubclass(self.obj.__class__, Series):
    return self.obj.__class__(result)

etc.

[TomAugspurger]

The PR I linked to earlier has stalled a bit. It'd be best to address calling groupby in a dedicated pull request if you're interested.

…

On Thu, Apr 16, 2020 at 5:04 AM pandichef ***@***.***> wrote: Fyi, this is still an issue on pandas 1.0.3. @TomAugspurger <https://github.com/TomAugspurger> I think there is a relatively quick fix that I'm using in a personal project... in DataFrameGroupBy, you have access to self.obj. So you can write a class decorator to implement the following logic at the end of every method in DataFrameGroupBy: if isinstance(method_result, DataFrame) and issubclass(self.obj.*class*, DataFrame): return self.obj.*class*(result) # elif isinstance(method_result, Series) and issubclass(self.obj.*class*, Series): return self.obj.*class*(result) etc. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#29442 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAKAOITJ362ISOPMVLP3SO3RM3JZPANCNFSM4JJ4VGDA> .

[pandichef]

Sure. I’d be happy to. But I’d like to make sure that my solution is acceptable at a high level before I start coding. Some might consider the decorator approach to be somewhat of a hack. Alternatively, I could manually change every “return DataFrame” into “return self.obj.__class__”. Please let me know what you think. On Thu, Apr 16, 2020 at 8:37 AM Tom Augspurger <notifications@github.com> wrote:

…

The PR I linked to earlier has stalled a bit. It'd be best to address calling groupby in a dedicated pull request if you're interested. On Thu, Apr 16, 2020 at 5:04 AM pandichef ***@***.***> wrote: > Fyi, this is still an issue on pandas 1.0.3. @TomAugspurger > <https://github.com/TomAugspurger> I think there is a relatively quick > fix that I'm using in a personal project... in DataFrameGroupBy, you have > access to self.obj. So you can write a class decorator to implement the > following logic at the end of every method in DataFrameGroupBy: > > if isinstance(method_result, DataFrame) and issubclass(self.obj.*class*, > DataFrame): > return self.obj.*class*(result) # > elif isinstance(method_result, Series) and issubclass(self.obj.*class*, > Series): > return self.obj.*class*(result) > etc. > > — > You are receiving this because you were mentioned. > Reply to this email directly, view it on GitHub > < #29442 (comment)>, > or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AAKAOITJ362ISOPMVLP3SO3RM3JZPANCNFSM4JJ4VGDA > > . > — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#29442 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AEHNEINEHFPNKEZZX25Z2GTRM33Z3ANCNFSM4JJ4VGDA> .

[TomAugspurger]

I'm not sure offhand.

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On Thu, Apr 16, 2020 at 11:04 AM pandichef ***@***.***> wrote: Sure. I’d be happy to. But I’d like to make sure that my solution is acceptable at a high level before I start coding. Some might consider the decorator approach to be somewhat of a hack. Alternatively, I could manually change every “return DataFrame” into “return self.obj.__class__”. Please let me know what you think. On Thu, Apr 16, 2020 at 8:37 AM Tom Augspurger ***@***.***> wrote: > The PR I linked to earlier has stalled a bit. It'd be best to address > calling groupby in a dedicated pull request if you're interested. > > On Thu, Apr 16, 2020 at 5:04 AM pandichef ***@***.***> > wrote: > > > Fyi, this is still an issue on pandas 1.0.3. @TomAugspurger > > <https://github.com/TomAugspurger> I think there is a relatively quick > > fix that I'm using in a personal project... in DataFrameGroupBy, you have > > access to self.obj. So you can write a class decorator to implement the > > following logic at the end of every method in DataFrameGroupBy: > > > > if isinstance(method_result, DataFrame) and issubclass(self.obj.*class*, > > DataFrame): > > return self.obj.*class*(result) # > > elif isinstance(method_result, Series) and issubclass(self.obj.*class*, > > Series): > > return self.obj.*class*(result) > > etc. > > > > — > > You are receiving this because you were mentioned. > > Reply to this email directly, view it on GitHub > > < > #29442 (comment) >, > > or unsubscribe > > < > https://github.com/notifications/unsubscribe-auth/AAKAOITJ362ISOPMVLP3SO3RM3JZPANCNFSM4JJ4VGDA > > > > . > > > > — > You are receiving this because you authored the thread. > Reply to this email directly, view it on GitHub > < #29442 (comment)>, > or unsubscribe > < https://github.com/notifications/unsubscribe-auth/AEHNEINEHFPNKEZZX25Z2GTRM33Z3ANCNFSM4JJ4VGDA > > . > — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#29442 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAKAOIVZGUMDXCLZTVLPJCLRM4UB3ANCNFSM4JJ4VGDA> .

[Japanuspus]

It appears that the commit responsible for the groupby regression is #34214, where object creation is done with type(self)(...) which does not call __finalize__ (or checks _constructor), which should be done according to the docs.

I will try to implement this internally and submit a pull request.