def particles(self):
        sim = self._sim.contents
        ps = []
        if self.testparticle>=0:
            N = 1
        else:
            N = sim.N-sim.N_var 
        ParticleList = Particle*N
        ps = ParticleList.from_address(ctypes.addressof(sim._particles.contents)+self.index*ctypes.sizeof(Particle))
        return ps