How I Model Aspects and Orbs in a Python Astrology Engine

I like working on aspect calculations because the astrology terminology disappears pretty quickly once you get into the code. At the calculation level, an aspect is basically: How close are two points on a circle to a configured angle? That turns the problem into geometry, tolerances and a few interesting edge cases. Start with angular distance Suppose two planets have longitudes: 12° 102° Their separation is 90°. That’s easy. But this pair is more interesting: 358° 2° A normal absolute difference gives you 356°. On a circle, they’re actually 4° apart. So one of the basic utilities looks conceptually like this: def angular_distance ( a : float , b : float ) -> float : delta = abs ( a - b ) % 360 return min ( delta , 360 - delta ) Now: angular_distance ( 358 , 2 ) returns: 4 That simple normalization is the base of the rest of the aspect system. Then define target angles For the major aspects, you’re comparing against angles such as: 0° conjunction 60° sextile 90° square 120° trine 180° opposition If everything had to be exact, the implementation would be trivial. But astrology uses orbs. So a separation of 92° can still be treated as a square depending on the calculation profile. The orb is basically: orb = abs ( actual_distance - target_angle ) Then: if orb <= allowed_orb : # aspect matched I keep orb rules in a profile This is one of those places where hidden constants are really tempting. Something like: MAX_ORB = 8 and move on. I prefer putting this kind of behavior into an explicit calculation profile. That way the result isn’t just: Venus square Saturn It can be understood as: Venus square Saturn under this aspect profile with this orb That makes the methodology easier to inspect and makes future changes much less messy. The engine reports geometry, not sentiment This was another boundary I wanted to keep clean. The core can calculate: planet A planet B aspect type orb phase It should not calculate: good bad easy terrible relationship Those are interpretation-