Here is a code sample showing the issue (indeed turning off blitting restores a correct behaviour): blue circle should be in front of red one

# -*- coding: utf-8 -*-
import matplotlib.pyplot as plt
import matplotlib.animation as animation
from math import sin, pi
fig = plt.figure()
ax = fig.add_subplot(111, autoscale_on=False, 
             xlim=(-2, 2), ylim=(-2, 2), aspect='equal')
circle_fg = plt.Circle((-0.5,0),1,color='b')
circle_fg.set_zorder(2)
ax.add_artist(circle_fg)
circle_bg = plt.Circle((0.5,0),1,color='r')
circle_bg.set_zorder(1)
ax.add_artist(circle_bg)
def init():
    circle_fg.radius = 0
    circle_bg.radius = 0
    return circle_fg, circle_bg
def animate(i):
    circle_fg.radius = 1
    circle_bg.radius = 1
    
    circle_fg.center = (-0.5, -sin(i*2*pi/50))
    circle_bg.center = (0.5, sin(i*2*pi/50))
    # order in return sequence determine draw order with blit=True, 
    # zorder property seems to be ignored
    return circle_fg, circle_bg
ani = animation.FuncAnimation(fig, animate, 200,
    interval=40, blit=True, init_func=init)
    
plt.show()

By the way, is there a cleaner way to define init function ? I alway have to put dubious code in it in order to get a clean empty background...

Sunbelt Computer Software

PL/B Language Development and Support

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artists zorder is ignored during animations #2959

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