MovieWriter ffmpeg unavailable; trying to use class ‘matplotlib.animation.PillowWriter’ instead

You can save animated plot as .gif with use of celluloid library:

from matplotlib import pyplot as plt
from celluloid import Camera
import numpy as np


# create figure object
fig = plt.figure()
# load axis box
ax = plt.axes()
# set axis limit
ax.set_ylim(0, 1)
ax.set_xlim(0, 10)

camera = Camera(fig)
for i in range(10):
    ax.scatter(i, np.random.random())
    plt.pause(0.1)
    camera.snap()

animation = camera.animate()
animation.save('animation.gif', writer='PillowWriter', fps=2)