wkp (Python binding)

Python package with a minimal Shapely-first API on top of the WKP Rust core.

Architecture

• src/lib.rs: the wkp._core extension, written with pyo3 and rust-numpy over wkp (core/)
• python/wkp/: the pure-Python package (Shapely conversion, GeometryFrame, contexts)
• Built with maturin as abi3 wheels: one wheel per platform works on every CPython from 3.10 up (including 3.14)
• The package version comes from the Cargo workspace (Cargo.toml at the repo root); a runtime check enforces core compatibility
• Large inputs are processed with the GIL released

Dependencies

• Python >= 3.10
• build: Rust (stable) and maturin (pulled in automatically by pip install)
• runtime: numpy, shapely
• dev/test: pytest, polyline

Install (dev)

From repo root:

pip install -e "bindings/python[dev]"     # or: cd bindings/python && maturin develop --release

Re-run after changing Rust code (Python changes are picked up directly).

Build

cd bindings/python
maturin build --release      # wheel for this platform, in ../../target/wheels
maturin sdist                # source distribution

Test

pytest bindings/python/tests

API

Geometry encode / decode

encode(geom, precision, *, ctx=None) -> str
decode(encoded, *, ctx=None) -> DecodedGeometry
decode_header(encoded) -> Header  # NamedTuple: (version, precision, dimensions, geometry_type)

encoded can be bytes, str (e.g. read from a text column or JSON) or any other bytes-like object. Encoders return str (use .encode("ascii") if you need bytes).

Supported geometries are Point, LineString (and LinearRing, which decodes as a LineString), Polygon, MultiPoint, MultiLineString and MultiPolygon, in 2D or 3D (XYZ). Geometries with M values raise ValueError: Shapely cannot rebuild them when decoding. Data with more than 3 dimensions can be encoded with encode_frame and decoded with decode_frame.

Limits

Precision is an integer from 0 to 63, and every |value| × 10^precision must be below 2^58 (e.g. ±2.8 × 10^12 at precision 5). Geometries and float streams have 1 to 16 dimensions, and values must be finite. Geometries must have the structure their type requires: one point for a Point, at least two per linestring, no empty parts.

Errors

Inputs wkp cannot encode or decode raise wkp.WkpError, a ValueError whose code is INVALID_ARGUMENT or MALFORMED_INPUT (the encoded data is not valid WKP). Arguments of the wrong type raise TypeError.

GeometryFrame — low-level flat representation

decode_frame(encoded, *, ctx=None) -> GeometryFrame
encode_frame(frame, *, ctx=None) -> str

GeometryFrame fields: version, precision, dimensions, geometry_type, coords (numpy float64 array, shape (n_points, dimensions)), segment_point_counts, group_segment_counts.

Methods: to_geometry() -> Shapely geometry, to_buffer() -> bytes, GeometryFrame.from_buffer(buf) -> GeometryFrame.

Float helpers

encode_floats(floats, precisions, *, ctx=None) -> str
decode_floats_array(encoded, precisions, *, ctx=None) -> np.ndarray  # flat (N*dims,) float64
decode_floats(encoded, precisions, *, ctx=None) -> np.ndarray        # shaped (N, dims) float64

decode_floats_array returns a flat 1D float64 array of interleaved values [x0, y0, x1, y1, ...] — a single allocation with no reshape. Use arr.tobytes() to treat it as a raw byte buffer for shipping over sockets or shared memory.

decode_floats wraps decode_floats_array and returns a (N, dims) 2D view (zero-copy reshape). Use .tolist() on the result if you need plain Python lists.

Context

Context()

A Context owns reusable native buffers. Buffers grow to fit the largest geometry processed, then stay allocated and get reused on subsequent calls — avoiding repeated allocations.

Thread-local (default) — one context per thread, created lazily, lives for the thread's lifetime:

encoded = encode(geom, precision)   # ctx=None uses the thread-local pool
decoded = decode(encoded)

Explicit reuse — create one context and pass it to a batch of calls; the pool is freed when the object is garbage-collected or explicitly deleted:

ctx = wkp.Context()
for geom in large_collection:
    encoded = encode(geom, precision, ctx=ctx)
    ...
del ctx  # in CPython, releases the native buffers once nothing else refers to ctx

A Context belongs to one thread at a time: using the same one from two threads concurrently raises RuntimeError: Already borrowed (use the default thread-local contexts, or one Context per thread). Inputs of 16k+ values are processed with the GIL released, so threads encoding or decoding large geometries run in parallel.

Per-call (no persistent memory) — create a fresh context for each call; buffers are freed as soon as the call returns:

encoded = encode(geom, precision, ctx=wkp.Context())

This costs one allocation/free per call but guarantees no native memory persists between calls — useful when peak RSS matters more than throughput.

Example

from shapely.geometry import LineString
from wkp import GeometryFrame, decode, decode_frame, encode

geom = LineString([
    (174.776, -41.289),
    (174.777, -41.290),
    (174.778, -41.291),
])

encoded = encode(geom, precision=6)
decoded = decode(encoded)

print(encoded)
print(decoded.geometry.wkt)

# Access the flat frame directly (useful for numpy / bulk processing)
frame = decode_frame(encoded)
print(frame.coords)          # numpy float64 array, shape (3, 2)
buf = frame.to_buffer()      # compact binary blob
frame2 = GeometryFrame.from_buffer(buf)  # round-trip
assert frame2 == frame

Benchmark

Full geometry encode/decode comparison against Shapely WKB/WKT:

python bindings/python/benchmark/benchmark.py --linestring-points=10000 --precisions=5 --max-iterations=1000 --max-duration=1

Flat-array API micro-benchmark (encode/decode/decode_frame/decode_floats_array):

python bindings/python/benchmark/bench_flat_api.py
python bindings/python/benchmark/bench_flat_api.py --points=50000 --iterations=200

Example results (wkp 0.6.0, Python 3.10, WSL2 on an i7-12700H, one core; x86-64, so the SIMD paths are used):

On the same machine, the 0.5.0 (nanobind + C core) build took 0.17 ms to encode and 0.18 ms to decode nz-coast (wkp-5p-str): 0.6.0 is about 2.8x / 3.6x faster.

Packaging / release

• abi3 wheels (manylinux and musllinux x86_64/aarch64, Windows x64/arm64, macOS x86_64/arm64) and the sdist are built in .github/workflows/python.yml with PyO3/maturin-action, then tested on Python 3.10 and 3.14.
• Release/publish runs from tag pushes or workflow_dispatch in .github/workflows/python.yml.
• Tag publish (recommended): push a tag in the exact format pypi-vX.Y.Z (for example pypi-v0.1.0).
• Publish order is always TestPyPI first, then PyPI.
• Python releases are binding-specific. Product-level GitHub releases use the separate wkp-vX.Y.Z tag flow.

Manual publish from GitHub

1. Open Actions -> Build and upload to PyPI.
2. Run workflow dispatch.
3. The workflow publishes to TestPyPI and then PyPI automatically.

If you only publish via git tags, manual dispatch is optional and can be removed.