MRRC: MARC Rust Crate

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 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
Benchmarked at ~4x pymarc throughput in Python, ~1M records/sec in Rust

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

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 |

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

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

License

MIT

Mrrc

Install / Use

README