ambers 0.2.2

Pure Rust SPSS .sav/.zsav reader with Polars DataFrame output

ambers

Pure Rust SPSS .sav/.zsav reader — Arrow-native, zero C dependencies.

Features

• Read .sav (bytecode) and .zsav (zlib) files
• Arrow RecordBatch output — zero-copy to Polars, DataFusion, DuckDB
• Rich metadata: variable labels, value labels, missing values, MR sets, measure levels
• Lazy reader via scan_sav() — returns Polars LazyFrame with projection and row limit pushdown
• No PyArrow dependency — uses Arrow PyCapsule Interface for zero-copy transfer
• One of the fastest SPSS readers — up to 2.5x faster than polars_readstat, 5–10x faster than pyreadstat
• Python + Rust dual API from a single crate

Installation

Python:

pip install ambers

Rust:

cargo add ambers

Quick Start

Python

import ambers as am

# Eager read — data + metadata
df, meta = am.read_sav("survey.sav")

# Lazy read — returns Polars LazyFrame
lf, meta = am.scan_sav("survey.sav")
df = lf.select(["Q1", "Q2", "age"]).head(1000).collect()

# Explore metadata
meta.summary()
meta.describe("Q1")
meta.value("Q1")

# Read metadata only (fast, skips data)
meta = am.read_sav_metadata("survey.sav")

Rust

use ambers::{read_sav, read_sav_metadata};

// Read data + metadata
let (batch, meta) = read_sav("survey.sav")?;
println!("{} rows, {} cols", batch.num_rows(), meta.number_columns);

// Read metadata only
let meta = read_sav_metadata("survey.sav")?;
println!("{}", meta.label("Q1").unwrap_or("(no label)"));

Metadata API (Python)

Method	Description
meta.summary()	Formatted overview: file info, type distribution, annotations
meta.describe("Q1")	Deep-dive into a single variable (or list of variables)
meta.diff(other)	Compare two metadata objects, returns MetaDiff
meta.label("Q1")	Variable label
meta.value("Q1")	Value labels dict
meta.format("Q1")	SPSS format string (e.g. "F8.2", "A50")
meta.measure("Q1")	Measurement level ("nominal", "ordinal", "scale")
meta.schema	Full metadata as a nested Python dict

All variable-name methods raise KeyError for unknown variables.

Streaming Reader (Rust)

let mut scanner = ambers::scan_sav("survey.sav")?;
scanner.select(&["age", "gender"])?;
scanner.limit(1000);

while let Some(batch) = scanner.next_batch()? {
    println!("Batch: {} rows", batch.num_rows());
}

Performance

Eager Read

All results return a Polars DataFrame. Average of 5 runs on Windows 11, Python 3.13, 24-core machine.

File	Size	Rows	Cols	ambers	polars_readstat	ambers vs prs	pyreadstat	pyreadstat mp (4w)	ambers vs pyreadstat
test_1 (bytecode)	0.2 MB	1,500	75	0.002s	0.004s	2.0x faster	0.010s	0.493s	5.0x faster
test_2 (bytecode)	147 MB	22,070	677	0.812s	0.991s	1.2x faster	3.564s	1.781s	4.4x faster
test_3 (uncompressed)	1.1 GB	79,066	915	0.509s	1.279s	2.5x faster	4.849s	2.764s	9.5x faster
test_4 (uncompressed)	0.6 MB	201	158	0.002s	0.004s	2.0x faster	0.018s	0.470s	9.0x faster
test_5 (uncompressed)	0.6 MB	203	136	0.002s	0.004s	2.0x faster	0.015s	0.454s	7.5x faster
test_6 (uncompressed)	5.4 GB	395,330	916	2.801s	1.809s	1.5x slower	24.199s	11.718s	8.6x faster

• vs polars_readstat: faster on 5 of 6 files — 1.2–2.5x faster (test_6 at 5.4 GB is 1.5x slower)
• vs pyreadstat: 4–10x faster across all file sizes
• vs pyreadstat multiprocess (4 workers): ambers single-threaded still faster on every file
• No PyArrow dependency — uses Arrow PyCapsule Interface for zero-copy transfer

pyreadstat multiprocess returns pandas; timing includes pl.from_pandas() conversion.

Lazy Read with Pushdown

scan_sav() returns a Polars LazyFrame. Unlike eager reads, it only reads the data you ask for:

File (size)	Full collect	Select 5 cols	Head 1000 rows	Select 5 + head 1000
test_2 (147 MB, 22K × 677)	0.903s	0.363s (2.5x)	0.181s (5.0x)	0.157s (5.7x)
test_3 (1.1 GB, 79K × 915)	0.700s	0.554s (1.3x)	0.020s (35x)	0.012s (58x)
test_6 (5.4 GB, 395K × 916)	3.062s	2.343s (1.3x)	0.022s (139x)	0.013s (236x)

On the 5.4 GB file, selecting 5 columns and 1000 rows completes in 13ms — 236x faster than reading the full dataset.

License

MIT