code: def particles_ascii(self, prec=8):
          
          s = ""
          for p in self.particles:
              s += (("%%.%de "%prec) * 8)%(p.m, p.r, p.x, p.y, p.z, p.vx, p.vy, p.vz) + "\n"
          if len(s):
              s = s[:-1]
          return s
docs: Returns an ASCII string with all particles' masses, radii, positions and velocities.
  
          Parameters
          ----------
          prec : int, optional
              Number of digits after decimal point. Default 8.