polars-io 0.4.2

Lazy and eager reading of Stata and SAS files into Polars

polars_io

Lazily read Stata (.dta), SAS (.sas7bdat, .xpt), fixed-width (.txt, .dat, etc.), and newline delimited (.txt) files in polars.

Installation

pip install polars_io
# Or:
uv add polars_io

Usage

import polars as pl
import polars_io as pio

# Lazily load a sas file.
lf = pio.scan_sas7bdat("huge_SAS_file.sas7bdat")

# Get its schema.
lf.collect_schema()

# Take a look at the first few rows.
lf.head().collect()

# Projection and predicate pushdown work!
(
    lf
    .filter(pl.col("birth_year").is_between(2000, 2010))
    .select(pl.col("usage").mean())
    .collect()
)

# Load fixed-width files.
col_locations = {"year": (10, 14), "population": (14, 20)}
pio.scan_fwf("populations.txt", col_locations)

# Eager versions of all functions are also available.
pio.read_dta("mortality_rates.dta")

See the documentation for more info.

Details

The Stata and SAS implementations make use of the readstat C library via the Python bindings provided by pyreadstat. For numeric types, reading uses zero-copy conversions from numpy -> pyarrow -> polars and should be faster and have lower memory overhead than reading the data into pandas and then calling pl.from_pandas (benchmarks welcome).

Contributing

PRs adding support for reading other formats are very welcome! (E.g., .Rdata, Stata .dct, SPSS files, etc.)

Known Issues

This packages fails to some read files with non-utf8 metadata (e.g., column labels, notes on .dta files). This is a known issue with upstream packages that is being worked on (see Roche/pyreadstat#298 and WizardMac/ReadStat#344).