# Polars 1.12.0 — Python Polars 1.12.0

- Product: Polars (https://whatsnew.fyi/product/polars)
- Vendor: Polars
- Date: 2024-10-27
- Version: 1.12.0
- Original notes: https://github.com/pola-rs/polars/releases/tag/py-1.12.0
- Permalink: https://whatsnew.fyi/product/polars/releases/1.12.0

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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- **deprecated** — Make some parameters of dt.add_business_days keyword-only
- **changed** — Address inadvertent quadratic behaviour in expand_columns
- **changed** — Move rolling_corr/cov to an actual implementation on Series
- **changed** — Don't split par if cast to categorical
- **added** — Implement nested Parquet writing for High-Precision Decimals
- **changed** — Improve read_database typing
- **changed** — Respect include_index for pandas series
- **added** — Add credential_provider argument to more read functions
- **added** — Add IPC sink in new streaming engine
- **added** — Support querying specific snapshot by id in scan_iceberg
- **fixed** — Include Array in to_physical
- **fixed** — Don't panic in SQL temporal string check; raise suitable ColumnNotFound error
- **fixed** — Properly raise on mean_horizontal with wrong dtypes
- **fixed** — Make output dtype known for list.to_struct when fields are passed
- **fixed** — Ensure sorted flag is unset after Int->String cast
- **fixed** — Fix row_index of batched reader
- **fixed** — Fix perfect groupby
- **fixed** — Correct wildcard expansion for functions
- **fixed** — Ensure struct eq/ne_missing also compares outer validity
- **fixed** — Fix incorrect reverse on struct containing NULLs

##### ⚠️ Deprecations

- Make some parameters of `dt.add_business_days` keyword-only (#19428)

##### 🚀 Performance improvements

- Address inadvertent quadratic behaviour in `expand_columns` (#19469)
- Move rolling\_corr/cov to an actual implementation on Series (#19466)
- Don't split par if cast to categorical (#19462)

##### ✨ Enhancements

- Implement nested Parquet writing for High-Precision Decimals (#19476)
- Improve `read_database` typing (#19444)
- Respect `include_index` for pandas series (#19453)
- Add `credential_provider` argument to more read functions (#19421)
- Add IPC sink in new streaming engine (#19431)
- Support querying specific snapshot by id in `scan_iceberg` (#19388)

##### 🐞 Bug fixes

- Include Array in `to_physical` (#19474)
- Don't panic in SQL temporal string check; raise suitable `ColumnNotFound` error (#19473)
- Properly raise on mean\_horizontal with wrong dtypes (#19472)
- Make output dtype known for `list.to_struct` when `fields` are passed (#19439)
- Address inadvertent quadratic behaviour in `expand_columns` (#19469)
- Ensure sorted flag is unset after Int->String cast (#19470)
- Fix row\_index of batched reader (#19465)
- Fix perfect groupby (#19461)
- Correct wildcard expansion for functions (#19449)
- Ensure struct `eq/ne_missing` also compares outer validity (#19443)
- Fix incorrect reverse on struct containing NULLs (#19446)
- Faulty `escape_regex` example (#19440)
- Capture groups should be ignored in replace when literal=True (#19413)
- Fix `ColumnNotFound` when using `pl.element()` inside `list.eval` (#19438)
- Updates error message in csv parser to recommend schema\_overrides instead of deprecated dtypes argument (#19416)
- Incorrect `.join(..., how="left").head(N)` if `N <= left_df.height()` and there are duplicate matches (#19422)
- Support Array type in more DataType methods (#19427)
- Bug in group\_tuples\_perfect, tail was not processed properly (#19417)
- Ensure that `ASCII*` table formats do not use the UTF8 ellipsis char when truncating rows/cols/values (#19404)

##### 📖 Documentation

- Fix docstrings for ATAN2 and ATAN2D SQL functions (#19351)

##### 🛠️ Other improvements

- Undo conflicting fix (#19463)
- Simplify rust side of `datetime` (#19459)
- Add tests for data mismatch on `read_json` (#19425)
- Remove code in `examples` folder in favor of the user guide (#19430)

Thank you to all our contributors for making this release possible!
@alexander-beedie, @cmdlineluser, @coastalwhite, @corleyma, @corwinjoy, @dvillaveces, @eitsupi, @gab23r, @janscholten, @nameexhaustion, @orlp, @ritchie46, @siddharth-vi, @stinodego and @wakabame