https://emmatyping.dev/2026-03-02T00:00:00-08:002026-03-02T00:00:00-08:002026-03-02T00:00:00-08:00Emma Smithtag:emmatyping.dev,2026-03-02:/announcing-ryaml-a-drop-in-compatible-python-yaml-parser.html

<blockquote> <p><strong>tl;dr</strong><br> <a href="https://github.com/emmatyping/ryaml">ryaml</a> is a YAML 1.1 parser that is both drop-in compatible and faster than PyYAML. And it's written in safe Rust too!</p> </blockquote> <p>Four (4) years ago, I wanted to make a YAML library that was fast and memory safe. This was originally a <a href="https://en.wiktionary.org/wiki/yak_shaving">yak shave</a> for another …</p>

<blockquote> <p><strong>tl;dr</strong><br> <a href="https://github.com/emmatyping/ryaml">ryaml</a> is a YAML 1.1 parser that is both drop-in compatible and faster than PyYAML. And it's written in safe Rust too!</p> </blockquote> <p>Four (4) years ago, I wanted to make a YAML library that was fast and memory safe. This was originally a <a href="https://en.wiktionary.org/wiki/yak_shaving">yak shave</a> for another project. I've forgotten which project since then! The result of that work was <a href="https://github.com/emmatyping/ryaml">ryaml</a>, a YAML parsing library for Python built on top of <a href="https://github.com/dtolnay/serde-yaml">serde-yaml</a>, which at the time was the go-to Rust yaml parsing library. Serde-yaml was fantastic to use at it allowed me to create the library in a performant manner while being very simple to implement. Together with serde-yaml I was able to use <a href="https://github.com/davidhewitt/pythonize">pythonize</a> by David Hewitt (lead PyO3 maintainer) to quickly convert from YAML text to Python objects and back again.</p> <p>The project was successful; ryaml was incredibly fast, and used Rust to parse scalar values like integers, strings, and floats. However, the initial version of ryaml had issues which I felt limited it from reaching where I wanted it to be.</p> <h2>Safety</h2> <p>Serde-yaml used <a href="https://github.com/dtolnay/unsafe-libyaml">libyaml-unsafe</a>, under the hood, an unsafe Rust port of libyaml using <a href="https://c2rust.com/">c2rust</a>. This was good for compatibility, (see the next section), but meant that ryaml's core was still unsafe. Unsafe Rust has a lot of benefits over C, but I wanted a majority of the parsing to happen in safe Rust to minimize the chance of memory-based exploits.</p> <h2>Compatibility</h2> <p>Serde-yaml did not support all of the features in YAML 1.1 that PyYAML does, <a href="https://github.com/dtolnay/serde-yaml/issues/91">such as binary types</a>. I wanted ryaml to be <em>drop-in compatible</em> with PyYAML eventually. To reach that goal would require handling a lot of extra parsing</p>