sparea 0.1.1

Compute the area of spherical polygons on the unit sphere.

sparea: Spherical Polygon Area

Python bindings for sparea_zig, a Zig library for computing the area of spherical polygons.

import math
from sparea import polygon_area

# Octant triangle: equator at lng=0, equator at lng=π/2, north pole.
# Vertices may be either (lat, lng) in radians or unit (x, y, z).
polygon_area([
    (0.0,         0.0),
    (0.0,         math.pi / 2),
    (math.pi / 2, 0.0),
])  # ≈ pi / 2

polygon_area([
    (1.0, 0.0, 0.0),
    (0.0, 1.0, 0.0),
    (0.0, 0.0, 1.0),
])  # ≈ pi / 2

The result is in steradians, in [0, 4π). Reverse the vertex order to get the complementary region (4π − interior).

Installing

Wheels aren't on PyPI yet, but you can install straight from the git repo with either pip or uv:

# regular pip
pip install git+https://github.com/ajfriend/sparea_py.git

# uv (project add)
uv add git+https://github.com/ajfriend/sparea_py.git

# uv (one-off in a venv)
uv pip install git+https://github.com/ajfriend/sparea_py.git

The Zig toolchain is pulled in automatically via the ziglang PyPI wheel listed in [build-system].requires — no host-level Zig install needed. The hatchling build hook (src/hatch_build.py) compiles libsparea.{dylib,so,dll} and bundles it into the wheel before pip installs it. The upstream sparea_zig source is fetched over the network from the URL pinned in src/zig/build.zig.zon.

See dev.md for architecture, layout, and contributor notes.