new_contents: class Particle:
      def __init__(self, x, y, ang_speed):
          self.x = x
          self.y = y
          self.ang_speed = ang_speed
  
  
  class ParticleSimulator:
      def __init__(self, particles):
          self.particles = particles
  
      def evolve(self, dt):
          time_step = 0.00001
          n_steps = int(dt/time_step)
  
          for i in range(n_steps):
              for p in self.particles:
                  # 1. calculate the direction
                  norm = (p.x**2+p.y**2)**0.5
                  v_x = (-p.y)/norm
                  v_y = p.x/norm
                  # 2. calculate the displacement
                  d_x = time_step * p.ang_speed * v_x
                  d_y = time_step * p.ang_speed * v_y
                  p.x += d_x
                  p.y += d_y
                  # 3. repeat for all the time_step
  
  
  
  def test_visualize():
      particles = [Particle(0.1, 0.5, +1),
              Particle(0.0, -0.5, -1),
              Particle(-0.1, -0.4, +3)]
      print('hallo alice')
  
  
  if __name__ == '__main__':
      test_visualize()
  
subject: test ssh key