pyfastyaml 0.1.0b1

Fast YAML parser for Python with C++/SIMD backend

FastYAML

Fast YAML parser for Python with C++/SIMD backend. 100–300× faster than PyYAML and ruamel.yaml. API compatible with PyYAML for typical config use cases (Kubernetes, Ansible, CI, Docker Compose).

Features

• High performance: C++17 implementation with AVX2 SIMD on x86 — orders of magnitude faster than pure-Python parsers
• PyYAML compatible API: loads(s), load(fp) — drop-in replacement for config loading
• Types: dict, list, str, int, float, bool, null, nested structures
• Indentation: 2-space (preferred), 4-space, tabs

Installation

pip install pyfastyaml

Requires Python 3.10+ and a C++ compiler with C++17 support.

Usage

import pyfastyaml

# Parse string
data = pyfastyaml.loads("""
key: value
nested:
  inner: 42
items:
  - a
  - b
""")
# {'key': 'value', 'nested': {'inner': 42}, 'items': ['a', 'b']}

# Parse file (path or file-like object)
data = pyfastyaml.load("config.yaml")

API matches PyYAML for common cases:

# Drop-in replacement
import pyfastyaml as yaml  # instead of import yaml
data = yaml.loads(yaml_string)
data = yaml.load("config.yaml")

Benchmark

Parsing time (μs, lower is better):

Size	FastYAML	PyYAML	ruamel	FastYAML vs PyYAML
Small (~200 B)	~2	~229	~377	~112× faster
Medium (~1.5 KB)	~7	~1,034	~1,777	~141× faster
Large (~15 KB)	~66	~11,153	~19,040	~170× faster
Realworld	~5	~841	~1,544	~161× faster

Run benchmarks:

pip install pytest-benchmark PyYAML ruamel.yaml
pytest tests/test_benchmark.py -v --benchmark-only

PyYAML Compatibility

FastYAML produces the same result as yaml.safe_load() for block-style YAML typical of configs. Compatibility tests included in tests/test_pyyaml_compat.py.

MVP Limitations

FastYAML targets config-style YAML (K8s, Ansible, CI, Docker Compose). Not supported:

• Flow syntax: [a, b, c], {a: 1, b: 2} — use block style instead
• Multiline strings: | (literal), > (folded)
• Anchors and aliases: &anchor, *alias
• Custom tags
• Multi-document (---)

Supported: block mappings, block sequences, scalars, comments, quoted strings, 2/4-space and tab indentation.

Development

pip install -e ".[dev]"
python setup.py build_ext --inplace
pytest tests/

Benchmark commands:

pytest tests/test_benchmark.py -v --benchmark-only
pytest tests/test_benchmark.py -v --benchmark-only --benchmark-autosave
pytest tests/test_benchmark.py -v --benchmark-only --benchmark-compare

Publishing (maintainers)

pip install build twine
python -m build
python -m twine upload dist/*

License

MIT