This is a follow-up of #31847 where we switched to absolute imports for Python files thanks to ruff but not Cython files. Maybe one day this can be enforced by cython-lint --ban-relative-imports, see MarcoGorelli/cython-lint#149

As an example PR you can look at #32316.

Here is the list of Cython files to tackle

• sklearn/cluster/_dbscan_inner.pyx MNT Switch to absolute imports in sklearn/cluster/_dbscan_inner.pyx #32316
• sklearn/cluster/_hdbscan/_linkage.pyx
• sklearn/cluster/_hdbscan/_reachability.pyx
• sklearn/cluster/_hdbscan/_tree.pxd
• sklearn/cluster/_hierarchical_fast.pxd
• sklearn/cluster/_hierarchical_fast.pyx
• sklearn/cluster/_k_means_common.pyx
• sklearn/cluster/_k_means_elkan.pyx
• sklearn/cluster/_k_means_lloyd.pyx
• sklearn/decomposition/_online_lda_fast.pyx
• sklearn/ensemble/_gradient_boosting.pyx @Ganasekhar-gif
• sklearn/ensemble/_hist_gradient_boosting/_binning.pyx
• sklearn/ensemble/_hist_gradient_boosting/_bitset.pxd
• sklearn/ensemble/_hist_gradient_boosting/_bitset.pyx
• sklearn/ensemble/_hist_gradient_boosting/common.pxd
• sklearn/ensemble/_hist_gradient_boosting/_gradient_boosting.pyx
• sklearn/ensemble/_hist_gradient_boosting/histogram.pyx
• sklearn/ensemble/_hist_gradient_boosting/_predictor.pyx
• sklearn/ensemble/_hist_gradient_boosting/splitting.pyx
• sklearn/feature_extraction/_hashing_fast.pyx
• sklearn/linear_model/_cd_fast.pyx
• sklearn/linear_model/_sag_fast.pyx.tp
• sklearn/linear_model/_sgd_fast.pyx.tp
• sklearn/manifold/_barnes_hut_tsne.pyx
• sklearn/manifold/_utils.pyx
• sklearn/metrics/cluster/_expected_mutual_info_fast.pyx
• sklearn/metrics/_dist_metrics.pxd.tp
• sklearn/metrics/_dist_metrics.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_argkmin_classmode.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_argkmin.pxd.tp
• sklearn/metrics/_pairwise_distances_reduction/_argkmin.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_base.pxd.tp
• sklearn/metrics/_pairwise_distances_reduction/_base.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_datasets_pair.pxd.tp
• sklearn/metrics/_pairwise_distances_reduction/_datasets_pair.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_middle_term_computer.pxd.tp
• sklearn/metrics/_pairwise_distances_reduction/_middle_term_computer.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_radius_neighbors_classmode.pyx.tp
• sklearn/metrics/_pairwise_distances_reduction/_radius_neighbors.pxd.tp
• sklearn/metrics/_pairwise_distances_reduction/_radius_neighbors.pyx.tp
• sklearn/metrics/_pairwise_fast.pyx
• sklearn/neighbors/_binary_tree.pxi.tp
• sklearn/neighbors/_partition_nodes.pxd
• sklearn/neighbors/_quad_tree.pxd
• sklearn/neighbors/_quad_tree.pyx
• sklearn/preprocessing/_csr_polynomial_expansion.pyx
• sklearn/preprocessing/_target_encoder_fast.pyx
• sklearn/svm/_liblinear.pyx
• sklearn/svm/_libsvm.pyx
• sklearn/svm/_libsvm_sparse.pyx
• sklearn/tree/_criterion.pxd
• sklearn/tree/_criterion.pyx
• sklearn/tree/_partitioner.pxd
• sklearn/tree/_splitter.pxd
• sklearn/tree/_splitter.pyx
• sklearn/tree/_tree.pxd
• sklearn/tree/_tree.pyx
• sklearn/tree/_utils.pxd
• sklearn/tree/_utils.pyx
• sklearn/utils/arrayfuncs.pyx
• sklearn/utils/_fast_dict.pxd
• sklearn/utils/_fast_dict.pyx MNT Switch to absolute imports in sklearn/utils/_fast_dict.pyx #32317
• sklearn/utils/_heap.pxd
• sklearn/utils/_heap.pyx
• sklearn/utils/murmurhash.pxd
• sklearn/utils/murmurhash.pyx
• sklearn/utils/_random.pxd
• sklearn/utils/_random.pyx
• sklearn/utils/_seq_dataset.pxd.tp
• sklearn/utils/_seq_dataset.pyx.tp
• sklearn/utils/_sorting.pxd
• sklearn/utils/sparsefuncs_fast.pyx
• sklearn/utils/_vector_sentinel.pxd
• sklearn/utils/_weight_vector.pyx.tp

I got the list of files from the following git grep command:

git grep -Pl 'from \..+import|import \.' **/*.pxd **/*.pyx **/*.tp