Fast Google Polyline Encoding and Decoding

Installation

uv add pypolyline
pip install pypolyline

Installing for local development

1. Ensure you have a copy of libpolylineffi and header.h from https://github.com/urschrei/polyline-ffi/releases, and it's in the src/pypolyline subdir
2. run uv sync --dev
3. run pytest .

Changes in pyx and pxd files, and the Rust library and header will bust the cache, triggering a rebuild when uv commands are run.

Supported Python Versions

All currently supported Python versions.

Supported Platforms

• Linux (manylinux*-compatible, x86_64 and aarch64)
• macOS (x86_64 and arm64)
• Windows 64-bit

Usage

Coordinates must be in (Longitude, Latitude) order

from pypolyline.cutil import encode_coordinates, decode_polyline

coords = [
            [52.64125, 23.70162],
            [52.64938, 23.70154],
            [52.64957, 23.68546],
            [52.64122, 23.68549],
            [52.64125, 23.70162]
         ]

# precision is 5 for Google Polyline, 6 for OSRM / Valhalla
polyline = encode_coordinates(coords, 5)
# polyline is 'ynh`IcftoCyq@Ne@ncBds@EEycB'
decoded_coords = decode_polyline(polyline, 5)

Error Handling

Failure to encode coordinates, or to decode a supplied Polyline, will raise a RuntimeError containing information about the invalid input.

How it Works

FFI and a Rust binary

Is It Fast

…Yes.
You can verify this by installing the polyline package, then running benchmarks.py, a calibrated benchmark using cProfile.
On an M2 MBP, The pure-Python test runs in ~2500 ms, the Flexpolyline benchmark runs in ~1500 ms and The Rust + Cython benchmark runs in around 80 ms (30 x and 17.5 x faster, respectively).

License

The Blue Oak Model Licence 1.0.0

Citing Pypolyline

If Pypolyline has been significant in your research, and you would like to acknowledge the project in your academic publication, we suggest citing it as follows (example in APA style, 7th edition):

Hügel, S. (2021). Pypolyline (Version X.Y.Z) [Computer software]. https://doi.org/10.5281/zenodo.5774925

In Bibtex format:

@software{Hugel_Pypolyline_2021,
author = {Hügel, Stephan},
doi = {10.5281/zenodo.5774925},
license = {MIT},
month = {12},
title = {{Pypolyline}},
url = {https://github.com/urschrei/simplification},
version = {X.Y.Z},
year = {2021}
}