mrrc 0.9.1

MRRC: A fast MARC library written in Rust with Python bindings

MRRC

A Rust library for reading, writing, and manipulating MARC bibliographic records, with Python bindings.

Note: This project was developed using agentic coding tools (amp and Claude) and uses beads_rust for agentic issue tracking. The package has not yet had extensive practical testing by humans and should be considered experimental.

Features

• Reads and writes ISO 2709 (MARC21) binary format
• Python bindings with pymarc-compatible API (minor differences documented)
• Multiple serialization formats: JSON, MARCXML, MARCJSON, CSV, Dublin Core, MODS, BIBFRAME
• MARC-8 and UTF-8 character encoding support
• Rust-core parsing with GIL release for multi-threaded Python workloads — roughly 8× pymarc on per-record reads in a recent single-host comparison; see benchmarks for the current three-way figures

Installation

Python (3.10+):

pip install mrrc
# or with uv:
uv add mrrc

Rust:

cargo add mrrc

Example

Python:

from mrrc import MARCReader

# Pass filename directly for best performance (releases GIL)
for record in MARCReader("records.mrc"):
    print(record.title)

File paths use pure Rust I/O, releasing Python's GIL for multi-threaded workloads. See the threading guide for details.

Rust:

use mrrc::MarcReader;
use std::fs::File;

let file = File::open("records.mrc")?;
let mut reader = MarcReader::new(file);
while let Some(record) = reader.read_record()? {
    if let Some(title) = record.title() {
        println!("{}", title);
    }
}

Documentation

• Getting Started
• Python Tutorials
• Rust Tutorials
• API Reference
• Migration from pymarc

Format Support

Format	Read	Write
ISO 2709	Yes	Yes
JSON	Yes	Yes
MARCJSON	Yes	Yes
MARCXML	Yes	Yes
CSV	-	Yes
Dublin Core	-	Yes
MODS	Yes	Yes
BIBFRAME	Yes	Yes

CSV and Dublin Core are write-only: both are lossy exports of a MARC record, so mrrc emits them but does not read them back. Bring your own reader if you need to import such data into MARC.

Full format reference

Platforms

Pre-built Python wheels are available for:

Platform	Architectures
Linux	x86_64, aarch64, i686
macOS	x86_64 (Intel), arm64 (Apple Silicon)
Windows	x64

Status

Experimental. The Python API aims for pymarc compatibility but has some differences; see the migration guide. Rust APIs may change between minor versions.

Roadmap

Version 0.9.1 is suitable for testing but remains experimental. Before a 1.0 release, we plan to complete:

1. Real-world data testing — Validate against large-scale MARC datasets from LOC, Internet Archive, and other sources to discover edge cases
2. Code review — Thorough review of the codebase, particularly the Rust core and PyO3 bindings
3. Performance analysis — Profile with production workloads, optimize bottlenecks, and update benchmark documentation

Contributing

Contributions are welcome — see the contributing guide for setup, testing, and pull request instructions. To report a security vulnerability, see the security policy.

License

MIT

Links

• Documentation
• PyPI
• crates.io
• GitHub