# Polars 1.35.0 — Python Polars 1.35.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2025-10-26
- Version: 1.35.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.35.0

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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- **added** — Add Expr.item to strictly extract a single value from an expression
- **added** — Add list.agg and arr.agg
- **added** — Implement {Expr,Series}.rolling_rank()
- **added** — Add arr.eval
- **added** — Add union() function for unordered concatenation
- **added** — Add name.replace to the set of column rename options
- **added** — Add separator to {Data,Lazy}Frame.unnest
- **added** — Add glob parameter to scan_ipc
- **added** — Add environment variable to roundtrip empty struct in Parquet
- **added** — Add streaming engine per-node metrics
- **added** — Add support for UInt128 to pyo3-polars
- **changed** — Stabilize decimal
- **changed** — Support ewm_mean() in streaming engine
- **changed** — Allow local scans on polars cloud (configurable)
- **changed** — Support MergeSorted in CSPE
- **changed** — Make Series init consistent with DataFrame init for string values declared with temporal dtype
- **changed** — Improve rolling_(sum|mean) accuracy
- **changed** — Allow duration strings with leading "+"
- **changed** — Support np.ndarray -> AnyValue conversion
- **fixed** — Fix incorrect join_asof on a casted expression

##### 🏆 Highlights

- Stabilize decimal (#25020)

##### 🚀 Performance improvements

- Bump foldhash to 0.2.0 and hashbrown to 0.16.0 (#25014)
- Lower `unique` to native group-by and speed up `n_unique` in group-by context (#24976)
- Better parallelize `take{_slice,}_unchecked` (#24980)
- Implement native `skew` and `kurtosis` in group-by context (#24961)
- Use native group-by aggregations for `bitwise_*` operations (#24935)
- 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

- Stabilize decimal (#25020)
- Support `ewm_mean()` in streaming engine (#25003)
- Improve row-count estimates (#24996)
- Remove filtered scan paths in IR when possible (#24974)
- Introduce remote Polars MCP server (#24977)
- Allow local scans on polars cloud (configurable) (#24962)
- Add `Expr.item` to strictly extract a single value from an expression (#24888)
- 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

- Re-enable CPU feature check before import (#25010)
- Implement `read_excel` workaround for fastexcel/calamine issue loading a column subset from a named table (#25012)
- Correctness `any(ignore_nulls)` and OOB in `all` (#25005)
- Streaming any/all with ignore\_nulls=False (#25008)
- Fix incorrect `join_asof` on a casted expression (#25006)
- Optimize memory on rolling groups in `ApplyExpr` (#24709)
- Fallback `Pyarrow` scan to in-memory engine (#24991)
- Make `Operator::swap_operands` return correct operators for `Plus`, `Minus`, `Multiply` and `Divide` (#24997)
- Capitalize letters after numbers in to\_titlecase (#24993)
- Preserve null values in `pct_change` (#24952)
- Raise length mismatch on `over` with sliced groups (#24887)
- Check duplicate name in transpose (#24956)
- Follow Kle

_[Truncated at 4000 characters — full notes: https://github.com/pola-rs/polars/releases/tag/py-1.35.0]_