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Dataframes powered by a multithreaded, vectorized query engine, written in Rust
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pola-rs/polars
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Documentation:Python -Rust -Node.js -R |StackOverflow:Python -Rust -Node.js -R |User guide |Discord
Polars is a DataFrame interface on top of an OLAP Query Engine implemented in Rust usingApache Arrow Columnar Format as the memorymodel.
- Lazy | eager execution
- Multi-threaded
- SIMD
- Query optimization
- Powerful expression API
- Hybrid Streaming (larger-than-RAM datasets)
- Rust | Python | NodeJS | R | ...
To learn more, read theuser guide.
>>>importpolarsaspl>>>df=pl.DataFrame(... {..."A": [1,2,3,4,5],..."fruits": ["banana","banana","apple","apple","banana"],..."B": [5,4,3,2,1],..."cars": ["beetle","audi","beetle","beetle","beetle"],... }... )# embarrassingly parallel execution & very expressive query language>>>df.sort("fruits").select(..."fruits",..."cars",...pl.lit("fruits").alias("literal_string_fruits"),...pl.col("B").filter(pl.col("cars")=="beetle").sum(),...pl.col("A").filter(pl.col("B")>2).sum().over("cars").alias("sum_A_by_cars"),...pl.col("A").sum().over("fruits").alias("sum_A_by_fruits"),...pl.col("A").reverse().over("fruits").alias("rev_A_by_fruits"),...pl.col("A").sort_by("B").over("fruits").alias("sort_A_by_B_by_fruits"),... )shape: (5,8)┌──────────┬──────────┬──────────────┬─────┬─────────────┬─────────────┬─────────────┬─────────────┐│fruits ┆cars ┆literal_stri ┆B ┆sum_A_by_ca ┆sum_A_by_fr ┆rev_A_by_fr ┆sort_A_by_B ││--- ┆--- ┆ng_fruits ┆--- ┆rs ┆uits ┆uits ┆_by_fruits ││str ┆str ┆--- ┆i64 ┆--- ┆--- ┆--- ┆--- ││ ┆ ┆str ┆ ┆i64 ┆i64 ┆i64 ┆i64 │╞══════════╪══════════╪══════════════╪═════╪═════════════╪═════════════╪═════════════╪═════════════╡│"apple" ┆"beetle" ┆"fruits" ┆11 ┆4 ┆7 ┆4 ┆4 ││"apple" ┆"beetle" ┆"fruits" ┆11 ┆4 ┆7 ┆3 ┆3 ││"banana" ┆"beetle" ┆"fruits" ┆11 ┆4 ┆8 ┆5 ┆5 ││"banana" ┆"audi" ┆"fruits" ┆11 ┆2 ┆8 ┆2 ┆2 ││"banana" ┆"beetle" ┆"fruits" ┆11 ┆4 ┆8 ┆1 ┆1 │└──────────┴──────────┴──────────────┴─────┴─────────────┴─────────────┴─────────────┴─────────────┘
>>>df=pl.scan_csv("docs/assets/data/iris.csv")>>>## OPTION 1>>># run SQL queries on frame-level>>>df.sql("""...SELECT species,... AVG(sepal_length) AS avg_sepal_length...FROM self...GROUP BY species...""").collect()shape: (3,2)┌────────────┬──────────────────┐│species ┆avg_sepal_length ││--- ┆--- ││str ┆f64 │╞════════════╪══════════════════╡│Virginica ┆6.588 ││Versicolor ┆5.936 ││Setosa ┆5.006 │└────────────┴──────────────────┘>>>## OPTION 2>>># use pl.sql() to operate on the global context>>>df2=pl.LazyFrame({..."species": ["Setosa","Versicolor","Virginica"],..."blooming_season": ["Spring","Summer","Fall"]...})>>>pl.sql("""... SELECT df.species,... AVG(df.sepal_length) AS avg_sepal_length,... df2.blooming_season... FROM df... LEFT JOIN df2 ON df.species = df2.species... GROUP BY df.species, df2.blooming_season... """).collect()
SQL commands can also be run directly from your terminal using the Polars CLI:
# run an inline SQL query> polars -c"SELECT species, AVG(sepal_length) AS avg_sepal_length, AVG(sepal_width) AS avg_sepal_width FROM read_csv('docs/assets/data/iris.csv') GROUP BY species;"# run interactively> polarsPolars CLI v0.3.0Type .helpfor help.> SELECT species, AVG(sepal_length) AS avg_sepal_length, AVG(sepal_width) AS avg_sepal_width FROM read_csv('docs/assets/data/iris.csv') GROUP BY species;
Refer to thePolars CLI repository for more information.
Polars is very fast. In fact, it is one of the best performing solutions available. See thePDS-H benchmarks results.
Polars is also very lightweight. It comes with zero required dependencies, and this shows in theimport times:
- polars: 70ms
- numpy: 104ms
- pandas: 520ms
If you have data that does not fit into memory, Polars' query engine is able to process your query(or parts of your query) in a streaming fashion. This drastically reduces memory requirements, soyou might be able to process your 250GB dataset on your laptop. Collect withcollect(engine='streaming')
to run the query streaming. (This might be a little slower, but it isstill very fast!)
Install the latest Polars version with:
pip install polars
We also have a conda package (conda install -c conda-forge polars
), however pip is the preferredway to install Polars.
Install Polars with all optional dependencies.
pip install'polars[all]'
You can also install a subset of all optional dependencies.
pip install'polars[numpy,pandas,pyarrow]'
See theUser Guide for more detailson optional dependencies
To see the current Polars version and a full list of its optional dependencies, run:
pl.show_versions()
Releases happen quite often (weekly / every few days) at the moment, so updating Polars regularly toget the latest bugfixes / features might not be a bad idea.
You can take latest release fromcrates.io
, or if you want to use the latest features /performance improvements point to themain
branch of this repo.
polars = {git ="https://github.com/pola-rs/polars",rev ="<optional git tag>" }
Requires Rust version>=1.80
.
Want to contribute? Read ourcontributing guide.
If you want a bleeding edge release or maximal performance you should compile Polars from source.
This can be done by going through the following steps in sequence:
- Install the latestRust compiler
- Installmaturin:
pip install maturin
cd py-polars
and choose one of the following:make build
, slow binary with debug assertions and symbols, fast compile timesmake build-release
, fast binary without debug assertions, minimal debug symbols, long compiletimesmake build-nodebug-release
, same as build-release but without any debug symbols, slightlyfaster to compilemake build-debug-release
, same as build-release but with full debug symbols, slightly slowerto compilemake build-dist-release
, fastest binary, extreme compile times
By default the binary is compiled with optimizations turned on for a modern CPU. SpecifyLTS_CPU=1
with the command if your CPU is older and does not support e.g. AVX2.
Note that the Rust crate implementing the Python bindings is calledpy-polars
to distinguish fromthe wrapped Rust cratepolars
itself. However, both the Python package and the Python module arenamedpolars
, so you canpip install polars
andimport polars
.
Extending Polars with UDFs compiled in Rust is easy. We expose PyO3 extensions forDataFrame
andSeries
data structures. See more inhttps://github.com/pola-rs/pyo3-polars.
Do you expect more than 2^32 (~4.2 billion) rows? Compile Polars with thebigidx
feature flag or,for Python users, installpip install polars-u64-idx
.
Don't use this unless you hit the row boundary as the default build of Polars is faster and consumesless memory.
Do you want Polars to run on an old CPU (e.g. dating from before 2011), or on anx86-64
build ofPython on Apple Silicon under Rosetta? Installpip install polars-lts-cpu
. This version of Polarsis compiled withoutAVX target features.
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Dataframes powered by a multithreaded, vectorized query engine, written in Rust