python-dateutil-rs 0.0.5

A Rust-backed port of python-dateutil

python-dateutil-rs

A high-performance Rust-backed port of python-dateutil (v2.9.0).

Status: Hybrid phase — easter, relativedelta, parser, and isoparser are rewritten in Rust via PyO3/maturin, delivering 1.3x–23.6x speedups. rrule and tz still delegate to python-dateutil.

Features

• Drop-in replacement for python-dateutil — same API, same behavior
• Rust-accelerated: easter, relativedelta, parser (parse / isoparse), weekday
• Full module coverage: parser, relativedelta, rrule, tz, easter, utils
• Comprehensive test suite inherited from the original project
• Benchmark infrastructure for side-by-side performance comparison (original vs Rust)
• Python 3.10–3.14 supported on Linux and macOS

Installation

pip install python-dateutil-rs

Usage

from dateutil_rs.parser import parse
from dateutil_rs.relativedelta import relativedelta
from dateutil_rs.rrule import rrule, MONTHLY
from dateutil_rs.tz import gettz, tzutc
from dateutil_rs.easter import easter

# Parse date strings
dt = parse("2024-01-15T10:30:00+09:00")

# Relative deltas
next_month = dt + relativedelta(months=+1)

# Recurrence rules
monthly = rrule(MONTHLY, count=5, dtstart=parse("2024-01-01"))

# Timezones
tokyo = gettz("Asia/Tokyo")
utc = tzutc()

# Easter
easter_date = easter(2024)

Development

Prerequisites

• Python 3.10+
• uv (recommended) or pip

Setup

git clone https://github.com/wakita181009/dateutil-rs.git
cd dateutil-rs
uv sync --extra dev

Running Tests

# Run the test suite
uv run pytest tests/ -x -q

# Run with coverage
uv run pytest tests/ --cov=dateutil

Linting

uv run ruff check src/ tests/
uv run ruff format --check src/ tests/

Benchmarks

Benchmarks compare three implementations: the original python-dateutil (PyPI), the local Python port, and the Rust extension (dateutil_rs) using pytest-benchmark.

Easter

Benchmark	python-dateutil	dateutil-rs (Rust)	Speedup
single call (Western)	0.49 µs	0.11 µs	4.3x
single call (Orthodox)	0.34 µs	0.06 µs	5.8x
single call (Julian)	0.29 µs	0.06 µs	4.9x
1000 years (Western)	436.74 µs	68.38 µs	6.4x
500 years × 3 methods	568.50 µs	107.30 µs	5.3x

RelativeDelta

Benchmark	python-dateutil	dateutil-rs (Rust)	Speedup
create simple	0.95 µs	0.18 µs	5.1x
add months to datetime	1.64 µs	0.18 µs	9.1x
subtract from datetime	2.96 µs	0.13 µs	22.2x
multiply by scalar	1.51 µs	0.08 µs	18.7x
diff between datetimes	2.84 µs	0.32 µs	9.0x
sequential add ×12	19.09 µs	1.74 µs	11.0x

Parser — parse()

Benchmark	python-dateutil	dateutil-rs (Rust)	Speedup
simple date	8.47 µs	5.27 µs	1.6x
datetime with tz	17.77 µs	6.39 µs	2.8x
fuzzy parsing	28.55 µs	8.27 µs	3.5x
10 various formats	168.25 µs	61.31 µs	2.7x

Parser — isoparse()

Benchmark	python-dateutil	dateutil-rs (Rust)	Speedup
isoparse date	0.80 µs	0.08 µs	10.6x
isoparse datetime+tz	3.04 µs	0.59 µs	5.1x
isoparse with µs	2.62 µs	0.11 µs	23.6x

Measured on Apple Silicon (M-series), Python 3.13, release build. Full results: benchmarks/RESULTS.md

# Install the original python-dateutil for comparison
uv pip install python-dateutil

# Run benchmarks
make bench

# Run and save results as JSON
make bench-save

Project Structure

dateutil-rs/
├── crates/dateutil-rs/    # Rust implementation (PyO3 extension)
│   └── src/
│       ├── lib.rs         # Crate root + #[pymodule] definition
│       ├── common.rs      # Weekday (MO–SU with N-th occurrence)
│       ├── easter.rs      # Easter date calculations
│       ├── relativedelta.rs # Relative date arithmetic
│       ├── parser/        # Date/time string parsing + ISO-8601
│       └── utils.rs       # Utility functions
├── python/dateutil_rs/    # Python package (maturin mixed layout)
│   ├── __init__.py        # Re-exports from Rust native module
│   ├── parser.py          # Rust parse/isoparse + fallback for custom parserinfo
│   ├── relativedelta.py   # Rust RelativeDelta
│   ├── easter.py          # Rust easter
│   ├── rrule.py           # Delegates to python-dateutil (not yet Rust)
│   ├── tz.py              # Delegates to python-dateutil (not yet Rust)
│   └── utils.py           # Rust within_delta + python-dateutil fallback
├── src/dateutil/          # Original python-dateutil v2.9.0 (reference only)
├── tests/                 # Test suite (~13k lines)
├── benchmarks/            # pytest-benchmark comparisons
├── .github/workflows/     # CI (lint + test matrix)
├── pyproject.toml
├── Makefile
└── LICENSE

Implementation Status

Module	Rust	Notes
easter	✅	4.3x–6.4x faster
relativedelta	✅	2.8x–22.2x faster
parser (parse)	✅	1.3x–3.5x faster; falls back to python-dateutil for custom parserinfo
parser (isoparse)	✅	5.1x–23.6x faster
common (Weekday)	✅
utils (within_delta)	✅	today() / default_tzinfo() still delegate to python-dateutil
rrule	❌	Delegates to python-dateutil
tz	❌	Delegates to python-dateutil

Roadmap

1. Python-only phase — Pure Python port with full test coverage ✅
2. Rust core + PyO3 bindings — easter, relativedelta, parser, weekday, utils ✅
3. Rust rrule — Rewrite recurrence rules in Rust
4. Rust tz — Rewrite timezone support in Rust
5. Release — Publish to crates.io and PyPI with pre-built wheels (manylinux, macOS, Windows)

License

MIT