# Polars 1.5.0 — Python Polars 1.5.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2024-08-14
- Version: 1.5.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.5.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.5.0

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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- **changed** — Improve binview extend/ifthenelse performance
- **changed** — Start on better Parquet delta decoding
- **changed** — Rechunk group-by __iter__
- **changed** — Tune jemalloc to not create muzzy pages
- **changed** — Reduce default async thread count
- **changed** — Make expensive selector expansion lazy
- **changed** — Use single threaded algorithms if only 1 core given
- **changed** — Use Arc<Vec<_>> instead of Arc<[_]> for paths and hive partitions
- **changed** — Use SIMD View from FixedSizeBinary
- **changed** — Use bitmask to filter Parquet predicate-pushdown items
- **changed** — Zerocopy buffers for FixedSizeBinary to BinaryView cast
- **added** — Create literals for datetime/date expressions
- **added** — Expose top-level has_header param for read_excel and read_ods
- **changed** — Raise on invalid is_between and improve error message quality
- **fixed** — Fix struct shift and list builder
- **fixed** — Don't load Parquet nested metadata
- **fixed** — Throw bigidx error for Parquet row-count
- **fixed** — Fix unpivot on empty df
- **fixed** — Ensure default values are included when saving/restoring the current Config state

##### 🚀 Performance improvements

- Improve binview extend/ifthenelse (#18164)
- Start on better Parquet delta decoding (#18049)
- Rechunk group-by \_\_iter\_\_ (#18162)
- Tune jemalloc to not create muzzy pages (#18148)
- Reduce default async thread count (#18142)
- Make expensive selector expansion lazy (#18118)
- Use single threaded algorithms if only 1 core given (#18101)
- Use `Arc<Vec<_>>` instead of `Arc<[_]>` for paths and hive partitions (#18066)
- SIMD View from `FixedSizeBinary` (#18059)
- Use bitmask to filter Parquet predicate-pushdown items (#17993)
- Zerocopy buffers for `FixedSizeBinary` to `BinaryView` cast (#18043)

##### ✨ Enhancements

- Create literals for datetime/date expressions (#18184)
- Create literals in 'datetime' expression (#18182)
- Expose top-level "has\_header" param for `read_excel` and `read_ods` (#18078)
- Raise on invalid 'is\_between' and improve error message quality (#18147)

##### 🐞 Bug fixes

- Fix struct shift and list builder (#18189)
- Don't load Parquet nested metadata (#18183)
- Throw bigidx error for Parquet row-count (#18154)
- Fix unpivot on empty df (#18179)
- Don't vertically parallelize cse contexts (#18177)
- Ensure default values are included when saving/restoring the current `Config` state (#18151)
- Properly handle empty Parquet row groups with no dictionary (#18161)
- Struct outer nullabillity (#18156)
- Fix pyarrow predicate pushdown regression (#18145)
- Prevent unwanted supertype cast in 'search\_sorted' (#18143)
- Parquet with `filter=None` (#18139)
- Don't raise when converting from pandas if index contains duplicate names when `include_index=False` (the default) (#18133)
- Fix cast Float to String where Float is not turn to Integer before turning to String (#18123)
- Don't remove leading whitespace in `read_csv` (#18131)
- Py-polars compilation with no features (#18129)
- String transform `to_titlecase` was too narrowly defined (#18122)
- Reading Parquet with Null dictionary page (#18112)
- When setting `write_excel` column totals, don't forget to include any row-total cols (#18042)
- Incorrect lazy CSV `select(len())` for compressed files (#18067)
- Fix `sink_ipc_cloud` panicking with runtime error (#18091)
- Properly write Parquet for sliced lists (#18073)
- Panic reading multiple CSV files from cloud (#18056)
- Fix `CloudWriter` to use buffer before making requests (#18027)
- Fix typos and remove trailing whitespace (#18024)
- Handle `cfg(feature)` for `shrink_dtype` (#18038)

##### 📖 Documentation

- Fix references to old methods in `lazy` docstring (#18178)
- Include PyCapsule Interface in DataFrame and Series API docs (#18174)
- Corrected example result in group\_by docs (#18169)
- Mention 'Array' in data types overview (#18060)
- Correct concat rechunk in user guide (#18080)
- Fix typo in title of Hugging Face docs page (#18097)
- Update pivot docstring for clarity (#18000)

##### 🛠️ Other improvements

- Remove unneeded growable (#18165)
- Update Cargo.lock to fix build error on Linux (#18153)
- Remove Nth,Wildcard from ExprIR and make conversion falllible (#18115)

Thank you to all our contributors for making this release possible!
@EricTulowetzke, @KDruzhkin, @MarcoGorelli, @Vincenthays, @alexander-beedie, @coastalwhite, @davanstrien, @deanm0000, @ember91, @kylebarron, @mcrumiller, @nameexhaustion, @orlp, @philss, @ritchie46 and @rosstitmarsh