Particle structure

A particle is represented by the reb_particle structure in C. The python class Particle is an abstraction of the reb_particle structure in C. We will refer to both the C structure and the python object interchangeably as the particle structure and particle object.

The particle object contains the following variables which can be directly manipulated:

double m

mass

double r

physical radius of the particle

double x, y, z, vx, vy, vz

position and velocity coordinates

const char* name

The name of the particle as a NULL terminated string. If the particle is part of a REBOUND simulation, then the memory of the name is managed by REBOUND. Do not set the name of a particle directly if it is in a REBOUND simulation. Use reb_particle_set_name() instead.

You can create a particle object which is not part of a REBOUND simulation.

CPython

struct reb_particle p = {.m=1., x=0., vy=0.};

p = rebound.Particle(m=1., x=0., vy=0.)

However, in most cases you will work with particles which have been added to a REBOUND simulation. You then access the particle using the simulation's particles array:

CPython

struct reb_simulation* r = reb_simulation_create();
// ... setup simulation, add particles ...
r->particles[0].x = 1;

sim = rebound.Simulation()
# ... setup simulation, add particles ... 
sim.particles[0].x = 1

Alternatively you can assign a name to particles and access them using the following syntax:

CPython

struct reb_simulation* r = reb_simulation_create();
reb_simulation_add_fmt(r, "m name", 1., "star"); 
reb_simulation_add_fmt(r, "a name", 1., "planet1"); 
struct reb_particle* p = reb_simulation_get_particle_by_name(r, "planet1");

sim = rebound.Simulation()
sim.add(m=1., name="star")
sim.add(a=1., name="planet1")
p = sim.particles["planet1"]