Almost every “how do I do astrology in code” answer points at pyswisseph - the Python bindings for the Swiss Ephemeris C library. It’s excellent. But it’s a C extension you compile, data files you ship, and chart logic you write yourself. A REST API removes all three. Here’s an honest comparison so you pick the right one.
What pyswisseph actually gives you
Section titled “What pyswisseph actually gives you”pyswisseph exposes the raw Swiss Ephemeris functions: swe_calc_ut,
swe_houses, and friends. You get maximum control and offline operation. In
return you take on:
- A C extension. It compiles on install: fine on your laptop, a recurring source of CI and Docker friction (build tools, wheels per platform/arch).
- Ephemeris data files. For full JPL precision you ship the
.se1files (tens of MB). The built-in Moshier mode avoids them at a small precision cost. - The astrology layer.
swe_calc_utreturns a longitude. House systems, aspect detection, dignities, chart assembly - you build all of it. - Licensing. The Swiss Ephemeris is dual-licensed (AGPL or a paid professional license). If you ship it inside a closed-source product, that’s a question you have to answer.
What a REST API gives you
Section titled “What a REST API gives you”AstroWay computes positions on its own servers, with no upstream API, and serves them over HTTP:
from astroway import Astroway, BirthData
aw = Astroway(api_key="aw_live_...")chart = aw.chart.compute(BirthData( date="1990-07-14", time="14:30:00", timezone_offset=3, latitude=50.45, longitude=30.52,))No compile step, no data files, no house-system code. You add a network round-trip and an API key, and get 865 endpoints (houses, aspects, synastry, transits, Vedic, Human Design) instead of just planet longitudes.
Side by side
Section titled “Side by side”| pyswisseph | REST API | |
|---|---|---|
| Install | Compiles a C extension | pip install, pure Python client |
| Data files | Ship .se1 for full precision | None - server-side |
| Chart logic | You write it | Endpoints return it |
| Offline | Yes | No (needs network) |
| Beyond longitudes | Build yourself | 865 endpoints |
| Accuracy | Swiss Ephemeris | Arc-second, verified against NASA JPL Horizons |
Decision guide
Section titled “Decision guide”- Use pyswisseph for an offline CLI, a notebook, a desktop app, or when you need the library to run with no network and you’re comfortable owning the data files, the chart code and the license question for your product.
- Use a REST API for a web app, a serverless function, or any service where
you don’t want a C build in your pipeline or ephemeris files in your image -
and where you’d rather call
synastryortransitsthan implement them.
Both give arc-second positions. The choice is about what you want to own.
Next steps
Section titled “Next steps”Des positions à la seconde d'arc en 4 lignes de code.
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