❌ Linting issues

This PR is introducing linting issues. Here's a summary of the issues. Note that you can avoid having linting issues by enabling pre-commit hooks. Instructions to enable them can be found here.

You can see the details of the linting issues under the lint job here

ruff check

ruff detected issues. Please run ruff check --fix --output-format=full locally, fix the remaining issues, and push the changes. Here you can see the detected issues. Note that the installed ruff version is ruff=0.11.7.

sklearn/preprocessing/_target_encoder.py:329:12: F821 Undefined name `groups`
    |
327 |         # overlapping validation folds, otherwise the fit_transform output will
328 |         # not be well-specified.
329 |         if groups is not None:
    |            ^^^^^^ F821
330 |             cv = GroupKFold(n_splits=self.cv)
331 |         elif self.target_type_ == "continuous":
    |

sklearn/preprocessing/_target_encoder.py:339:47: F821 Undefined name `groups`
    |
337 |         # Only validate non-approved splitters to avoid overhead
338 |         if not isinstance(cv, APPROVED_CV_SPLITTERS):
339 |             _validate_cv_no_overlap(cv, X, y, groups)
    |                                               ^^^^^^ F821
340 |
341 |         # If 'multiclass' multiply axis=1 by num classes else keep shape the same
    |

sklearn/preprocessing/_target_encoder.py:350:51: F821 Undefined name `groups`
    |
348 |             X_out = np.empty_like(X_ordinal, dtype=np.float64)
349 |
350 |         for train_idx, test_idx in cv.split(X, y, groups):
    |                                                   ^^^^^^ F821
351 |             X_train, y_train = X_ordinal[train_idx, :], y_encoded[train_idx]
352 |             y_train_mean = np.mean(y_train, axis=0)
    |

Found 3 errors.

_{Generated for commit: bb0918d. Link to the linter CI: here}

This needs to be using metadata routing to route groups, and isn't at the moment.

We also decided if the user wants to user groups, they need to explicitly pass a grouped cv object, and we won't do that for the user.

Note that handling metadata routing is not necessarily easy and it's okay if you don't want to continue the work.

I understand that the preferred direction is to handle groups through metadata routing and require users to explicitly pass a grouped CV object, rather than switching automatically inside TargetEncoder.

I’d be very interested in contributing to this area, but I’ll need to study the metadata routing system more deeply before I can contribute meaningfully here. In the meantime, others are of course welcome to continue building on this PR.

Thanks again to @adrinjalali, and @thomasjpfan for the guidance!

Thanks, @adrinjalali! I’ll go through the metadata routing documentation and past PRs to get a better handle on it. I’ll reach out if I need any guidance.

Thanks for all the work here @samruddhibaviskar11 but from what it looks like, it seems it's best if you tackle easier issues before getting to this one. So closing the PR.