# Polars 1.41.1 — Python Polars 1.41.1

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2026-05-27
- Version: 1.41.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.41.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.41.1

What's New is an index, not a publisher: every entry below links to the vendor's own release notes, which are the authoritative source. Entries are labelled where they are hand-curated sample data, pre-releases, or drawn from a secondary source such as a developer blog.

Reuse: the summaries, labels and curation here are © What's New. Quote freely with attribution and a link back; wholesale republication of the corpus is not permitted — terms: https://whatsnew.fyi/terms. The vendors' own release notes remain their publishers'.

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- **changed** — Improve performance of agg_n_unique with adaptive size dispatch to hashset or radix sort and capacity-aware reset
- **added** — Allow deeper expressions
- **fixed** — Raise length mismatch in multiple sort_by in group_by
- **fixed** — Respect min_samples for rolling_by ops with nulls
- **fixed** — Fix memory usage regression affecting TPCH Q22
- **added** — Add POLARS_ALLOW_NESTED_CSPE env var and make nested CSPE opt-in
- **fixed** — Post-apply residual pyarrow predicates
- **fixed** — Fix loss of precision for smaller floating types
- **fixed** — Fix filter at scan dropped in CSPE filter pushdown
- **fixed** — Fix portstate assertion error on is_in
- **fixed** — Fix incorrect when/then after forward fill / reverse in groupby
- **fixed** — Accept empty Thrift list encoded as bare 0x00 byte in parquet metadata
- **fixed** — Stabilize object store credentialprovider cache key

##### 🚀 Performance improvements

- Adaptive size dispatch to hashset or radix sort + capacity-aware reset in `agg_n_unique` (#27719)

##### ✨ Enhancements

- Allow deeper expressions (#27768)

##### 🐞 Bug fixes

- Raise length mismatch in multiple `sort_by` in `group_by` (#27772)
- Respect min\_samples for rolling\_by ops with nulls (#27706)
- Fix memory usage regression affecting TPCH Q22 (#27758)
- Add `POLARS_ALLOW_NESTED_CSPE` env var and make nested CSPE opt-in (#27765)
- Post-apply residual pyarrow predicates (#27764)
- Fix loss of precision for smaller floating types(#27662) (#27732)
- Filter at scan dropped in CSPE filter pushdown (#27763)
- Fix portstate assertion error on is\_in (#27757)
- Fix incorrect when/then after forward fill / reverse in groupby (#27745)
- Accept empty Thrift list encoded as bare 0x00 byte in parquet metadata (#27754)
- Stabilize object store `credentialprovider` cache key (#27712)
- Add to `merge_sorted` docs that the input must be nulls first (#27743)

##### 📖 Documentation

- Docs fixes (#27766)
- Sync from Polars Cloud (#27751)
- Add to `merge_sorted` docs that the input must be nulls first (#27743)

##### 🛠️ Other improvements

- Attribute annotations for `CatalogCredentialProvider` (#27739)
- Solve `type: ignore` in \_AioDataFrameResult (#27311)
- Remove dead code in `_write_utils.py` (#27721)
- Remove unnecessary ``not isinstance(v, DataType)`` check (#27723)

Thank you to all our contributors for making this release possible!
@EndPositive, @JakubValtar, @MarcoGorelli, @NicoOhR, @azimafroozeh, @carnarez, @dsprenkels, @jorenham, @kdn36, @nameexhaustion, @orlp and @ritchie46