API add named_transformers attribute to FeatureUnion #20331

crflynn · 2021-06-23T00:59:32Z

Reference Issues/PRs

What does this implement/fix? Explain your changes.

This provides an attribute named_transformers to FeatureUnion, allowing access to estimators in a similar way as named_steps on Pipeline.

e.g.

fs = FeatureUnion([("scaler", StandardScaler()), ("func", FunctionTransformer()])

# access via named attribute
scaler = fs.named_transformers.scaler

# indexing by name
scaler = fs.named_transformers["scaler"]

Any other comments?

ogrisel · 2021-06-23T08:35:41Z

That sounds like a legit need and fix. However I am not sure about the name. For the ColumnTransformer the matching attribute it named named_transformers_. I think we should use the same name for consistency.

ogrisel · 2021-06-23T08:36:43Z

Note: the test failure is unrelated and has been fixed in the main branch.

crflynn · 2021-06-23T14:14:47Z

I was going for consistency with Pipeline i.e. steps -> named_steps, although I think named_transformers (no trailing underscore) might be better.

ogrisel · 2021-06-23T16:57:22Z

I was going for consistency with Pipeline i.e. steps -> named_steps, although I think named_transformers (no trailing underscore) might be better.

Pipeline is a bit of an outlier. If the goal it to access the transformers after fitting them, then it makes sense to expose those as a fitted attribute with the trailing _ to be consistent with the scikit-learn API conventions.

crflynn · 2021-06-23T17:10:16Z

As with Pipeline, I'd just like to navigate the hierarchy more easily in general, regardless of whether or not it's fitted. For further motivation, accessing estimators like this helps a lot when debugging in my experience.

ogrisel · 2021-06-23T17:13:07Z

I am pretty sure the other reviewers will agree with me that we prefer consistency with the ColumnTransformer's named attribute in this case. The fact that the named steps of Pipeline are not published as a standard scikit-learn fitted attribute is an hard-to-fix historical artifact that we should not replicate.

sklearn/pipeline.py

crflynn · 2021-06-23T17:25:11Z

I've made the requested changes, although I still find it a bit awkward to be consistent with ColumnTransformer over Pipeline and inconsistent with attributes in general.

ogrisel · 2021-06-23T17:34:40Z

All the non-trailing-_ public attributes of scikit-learn estimators should be untouched constructor parameters which is not the case for this one.

crflynn · 2021-06-23T17:35:52Z

All the non-trailing-_ public attributes of scikit-learn estimators should be untouched constructor parameters which is not the case for this one.

That makes more sense. Thanks for the clarification.

ogrisel

LGTM!

Thanks for you contribution and bearing with me @crflynn!

doc/whats_new/v1.0.rst

sklearn/pipeline.py

thomasjpfan

Thank you for the PR @crflynn!

I added a comment for @ogrisel to discuss a potential API issue.

thomasjpfan · 2021-06-24T14:33:34Z

sklearn/pipeline.py

+    @property
+    def named_transformers_(self):


@ogrisel named_transformers_ uses the naming convention for an (fitted) attribute but is defined before calling fit. I am not sure what to do for FeatureUnion since it overwrites transformer_list during fit. (unlike ColumnTransformer)

I hadn't realized that. Would something like this be more conformant?

@property def named_transformers_(self): try: check_is_fitted(self) except NotFittedError: return Bunch(**dict(self.transformer_list)) return Bunch(**dict(self.transformer_list_)) def _update_transformer_list(self, transformers): transformers = iter(transformers) # use a fit attrib, and reference this when fitting self.transformer_list_ = [(name, old if old == 'drop' else next(transformers)) for name, old in self.transformer_list]

Returning something when unfitted might also be technically incorrect, however. This would also be a breaking change.

@thomasjpfan do you think that it could be better to have a named_transformers with the same semantic than in Pipeline? Our API is broken there and I am not sure that using the _ is actually a good idea then.

do you think that it could be better to have a named_transformers with the same semantic than in Pipeline?

I would be okay with a named_transformers to be consistent with Pipeline's named_steps:

scikit-learn/sklearn/pipeline.py

Lines 247 to 249 in 9580530

def named_steps(self):

# Use Bunch object to improve autocomplete

return Bunch(**dict(self.steps))

Agreed. @crflynn Would you mind make the change?

I've updated to reflect this. Tangentially, any plan to correct the API on Pipeline/FeatureUnion?

Tangentially, any plan to correct the API on Pipeline/FeatureUnion?

The work was started here: #8350

(I also remember speaking with @glemaitre about this in 2019 😅 )

Yep, it is even older than 2019. The difficulties in correcting the API come that we might have allowed some use-cases that the correct API would not allow. So we kind of need to think about all of them and provide the correct API but as well support of all previous use-cases.

glemaitre

LGTM. I will not merge since the +1 of @ogrisel was standing with another API.

sklearn/tests/test_pipeline.py

Co-authored-by: Guillaume Lemaitre <[email protected]>

cmarmo · 2022-05-10T22:16:38Z

@ogrisel would you be available for a final review? Thanks!

ogrisel

Re-reading the code of FeatureUnion I had completely forgotten that it was suffering from the same historical design flows as the Pipeline class.

Ok for being consistent with the Pipeline behavior for the time being...

sklearn/pipeline.py

ogrisel · 2022-10-25T09:11:53Z

Let's wait for the CI to complete and then merge.

) Co-authored-by: Guillaume Lemaitre <[email protected]> Co-authored-by: Olivier Grisel <[email protected]>

add indexing to FeatureUnion

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github-actions bot added the module:pipeline label Jun 23, 2021

Merge branch 'scikit-learn:main' into feature-union-indexing

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crflynn added 2 commits June 23, 2021 13:18

update attribute name

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rm getitem and use trailing underscore

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fix test name

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fix test name

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crflynn changed the title ~~API add named_transformer_list and indexing to FeatureUnion~~ API add named_transformers_ attribute to FeatureUnion Jun 23, 2021

update changelog and docs

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crflynn and others added 3 commits July 23, 2021 18:07

rm trailing underscore

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fix doc

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Merge branch 'scikit-learn:main' into feature-union-indexing

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crflynn changed the title ~~API add named_transformers_ attribute to FeatureUnion~~ API add named_transformers attribute to FeatureUnion Jul 23, 2021

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Update sklearn/tests/test_pipeline.py

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Co-authored-by: Guillaume Lemaitre <[email protected]>

cmarmo added the Waiting for Reviewer label May 10, 2022

cmarmo added Waiting for Second Reviewer First reviewer is done, need a second one! and removed Waiting for Reviewer labels Oct 20, 2022

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ogrisel added 3 commits October 25, 2022 11:02

Update versionadded

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Merge branch 'main' into feature-union-indexing

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ogrisel merged commit ff33ffb into scikit-learn:main Oct 25, 2022

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API add named_transformers attribute to FeatureUnion (scikit-learn#20331

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) Co-authored-by: Guillaume Lemaitre <[email protected]> Co-authored-by: Olivier Grisel <[email protected]>

andportnoy pushed a commit to andportnoy/scikit-learn that referenced this pull request Nov 5, 2022

API add named_transformers attribute to FeatureUnion (scikit-learn#20331

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) Co-authored-by: Guillaume Lemaitre <[email protected]> Co-authored-by: Olivier Grisel <[email protected]>

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API add named_transformers attribute to FeatureUnion #20331

API add named_transformers attribute to FeatureUnion #20331

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	def named_steps(self):
	# Use Bunch object to improve autocomplete
	return Bunch(**dict(self.steps))

API add named_transformers attribute to FeatureUnion #20331

API add named_transformers attribute to FeatureUnion #20331

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crflynn commented Jun 23, 2021 • edited Loading

Reference Issues/PRs

What does this implement/fix? Explain your changes.

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