Matplotlib animate showing up empty plot even while using a basic tutorials

Question

I used the exact code from this StackOverflow question.

When I run this code, this is all I see:

I wish I had more details to provide but I'm confused as to why even this simple example is not showing up correctly.

Answer 1

As I see you use Jupyter Notebook, so you should run this command to to show up matplotlib results:

%matplotlib inline

also you need there to use HTML from IPython.display. Then pass your animation converted to html video to this HTML function:

HTML(anim.to_html5_video())

There is a full example below. I'm using the code you cited in your question and changed it little bit:

import numpy as np
import matplotlib.pyplot as plt
from matplotlib import animation
from IPython.display import HTML


dt = 0.01
tfinal = 5.0
x0 = 0


sqrtdt = np.sqrt(dt)
n = int(tfinal/dt)
xtraj = np.zeros(n+1, float)
trange = np.linspace(start=0,stop=tfinal ,num=n+1) 
xtraj[0] = x0

for i in range(n):
    xtraj[i+1] = xtraj[i] + np.random.normal() 

x = trange
y = xtraj

# animation line plot example

fig = plt.figure(4)
ax = plt.axes(xlim=(-5, 5), ylim=(0, 5))
line, = ax.plot([], [], lw=2)

def init():
    line.set_data([], [])
    return line,

def animate(i):
    line.set_data(x[:i], y[:i])
    return line,

anim = animation.FuncAnimation(fig, animate, init_func=init, frames=len(x)+1,interval=200, blit=False)


HTML(anim.to_html5_video())