importmatplotlib.pyplotaspltimportnumpyasnpfrommatplotlib.animationimportFuncAnimation# Fixing random state for reproducibilitynp.random.seed(19680801)# Create new Figure and an Axes which fills it.fig=plt.figure(figsize=(7,7))ax=fig.add_axes((0,0,1,1),frameon=False)ax.set_xlim(0,1),ax.set_xticks([])ax.set_ylim(0,1),ax.set_yticks([])# Create rain datan_drops=50rain_drops=np.zeros(n_drops,dtype=[('position',float,(2,)),('size',float),('growth',float),('color',float,(4,))])# Initialize the raindrops in random positions and with# random growth rates.rain_drops['position']=np.random.uniform(0,1,(n_drops,2))rain_drops['growth']=np.random.uniform(50,200,n_drops)# Construct the scatter which we will update during animation# as the raindrops develop.scat=ax.scatter(rain_drops['position'][:,0],rain_drops['position'][:,1],s=rain_drops['size'],lw=0.5,edgecolors=rain_drops['color'],facecolors='none')defupdate(frame_number):# Get an index which we can use to re-spawn the oldest raindrop.current_index=frame_number%n_drops# Make all colors more transparent as time progresses.rain_drops['color'][:,3]-=1.0/len(rain_drops)rain_drops['color'][:,3]=np.clip(rain_drops['color'][:,3],0,1)# Make all circles bigger.rain_drops['size']+=rain_drops['growth']# Pick a new position for oldest rain drop, resetting its size,# color and growth factor.rain_drops['position'][current_index]=np.random.uniform(0,1,2)rain_drops['size'][current_index]=5rain_drops['color'][current_index]=(0,0,0,1)rain_drops['growth'][current_index]=np.random.uniform(50,200)# Update the scatter collection, with the new colors, sizes and positions.scat.set_edgecolors(rain_drops['color'])scat.set_sizes(rain_drops['size'])scat.set_offsets(rain_drops['position'])return[scat]# Construct the animation, using the update function as the animation director.animation=FuncAnimation(fig,update,interval=10,save_count=100,blit=True)plt.show()

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