# Polars 1.35.0-beta.1 — Python Polars 1.35.0-beta.1

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2025-10-19
- Version: 1.35.0-beta.1
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0-beta.1
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.0-beta.1
- Labels: Pre-release

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** — Address group_by_dynamic slowness in sparse data
- **changed** — Push filters to PyIceberg
- **changed** — Implement native filter/drop_nulls/drop_nans in group-by context
- **changed** — Implement cumulative_eval using the group-by engine
- **changed** — Prevent generation of copies of Dataframes in DslPlan serialization
- **changed** — Implement native null_count, any and all group-by aggregations
- **changed** — Speed up reverse in group-by context
- **changed** — Prune unused categorical values when exporting to arrow/parquet/IPC/pickle
- **changed** — Lower approx_n_unique to the streaming engine
- **changed** — Duration/interval string parsing is 2-5x faster
- **changed** — Use native reducer for first/last on Decimals, Categoricals and Enums
- **added** — Add environment variable to roundtrip empty struct in Parquet
- **added** — Add glob parameter to scan_ipc
- **added** — Add list.agg and arr.agg
- **added** — Implement {Expr,Series}.rolling_rank()
- **added** — Add arr.eval
- **added** — Add separator to {Data,Lazy}Frame.unnest
- **added** — Add union() function for unordered concatenation
- **added** — Add name.replace to the set of column rename options
- **fixed** — Fix repeated with_row_index() after scan() silently ignored

##### 🚀 Performance improvements

- Address `group_by_dynamic` slowness in sparse data (#24916)
- Push filters to PyIceberg (#24910)
- Native `filter/drop_nulls/drop_nans` in group-by context (#24897)
- Implement `cumulative_eval` using the group-by engine (#24889)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Implement native `null_count`, `any` and `all` group-by aggregations (#24859)
- Speed up `reverse` in group-by context (#24855)
- Prune unused categorical values when exporting to arrow/parquet/IPC/pickle (#24829)
- Don't check duplicates on streaming simple projection in release mode (#24830)
- Lower approx\_n\_unique to the streaming engine (#24821)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Use native reducer for `first/last` on Decimals, Categoricals and Enums (#24786)
- Implement indexed method for `BitMapIter::nth` (#24766)
- Pushdown slices on plans within unions (#24735)

##### ✨ Enhancements

- Add environment variable to roundtrip empty struct in Parquet (#24914)
- Fast-count for `scan_iceberg().select(len())` (#24602)
- Add `glob` parameter to `scan_ipc` (#24898)
- Prevent generation of copies of `Dataframe`s in `DslPlan` serialization (#24852)
- Add `list.agg` and `arr.agg` (#24790)
- Implement `{Expr,Series}.rolling_rank()` (#24776)
- Don't require PyArrow for `read_database_uri` if ADBC engine version supports PyCapsule interface (#24029)
- Make `Series` init consistent with `DataFrame` init for string values declared with temporal dtype (#24785)
- Support MergeSorted in CSPE (#24805)
- Duration/interval string parsing optimisation (2-5x faster) (#24771)
- Recursively apply CSPE (#24798)
- Add streaming engine per-node metrics (#24788)
- Add `arr.eval` (#24472)
- Drop PyArrow requirement for non-batched usage of `read_database` with the ADBC engine and support `iter_batches` with the ADBC engine (#24180)
- Improve rolling\_(sum|mean) accuracy (#24743)
- Add `separator` to `{Data,Lazy}Frame.unnest` (#24716)
- Add `union()` function for unordered concatenation (#24298)
- Add `name.replace` to the set of column rename options (#17942)
- Support `np.ndarray -> AnyValue` conversion (#24748)
- Allow duration strings with leading "+" (#24737)
- Drop now-unnecessary post-init "schema\_overrides" cast on `DataFrame` load from list of dicts (#24739)
- Add support for UInt128 to pyo3-polars (#24731)

##### 🐞 Bug fixes

- Properly release the GIL for `read_parquet_metadata` (#24922)
- Broadcast `partition_by` columns in `over` expression (#24874)
- Clear index cache on stacked `df.filter` expressions (#24870)
- Fix 'explode' mapping strategy on scalar value (#24861)
- Fix repeated `with_row_index()` after `scan()` silently ignored (#24866)
- Correctly return min and max for enums in groupby aggregation (#24808)
- Refactor `BinaryExpr` in `group_by` dispatch logic (#24548)
- Fix aggstate for `gather` (#24857)
- Keep scalars for length preserving functions in `group_by` (#24819)
- Have `range` feature depend on `dtype-array` feature (#24853)
- Fix duplicate select panic (#24836)
- Inconsistency of list.sum() result type with None values (#24476)
- Division by zero in Expr.dt.truncate (#24832)
- Potential deadlock in \_\_arrow\_c\_stream\_\_ (#24831)
- Allow double aggregations in group-by contexts (#24823)
- Series.shrink\_dtype for i128/u128 (#24833)
- Fix dtype in `EvalExpr` (#24650)
- Allow aggregations on `AggState::LiteralScalar` (#24820)
- Dispatch to `group_aware` for fallible expressions with masked out elements (#24815)
- Fix error for `arr.sum()` on small integer Array dtypes containing nulls (#24478)
- Fix regression on `write_database()` to Snowflake due to unsupported string view type (#24622)
- Fix XOR did not follow kleene when one side is unit-length (#24810)
- Make `Series` init consistent with `DataFrame` init for string values declared with temporal dtype (#24785)
- Incorrect precision in Series.str.to\_decimal (#24804)
- Use `overl

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