title: Animating a 2D random walk, Python
body: <p>I am trying to animate a random walk in 2 dimensions. I've been able to do this using turtle, but I want to learn this animation package. When I run the following code, I get a blank plane and I'm not sure why. Any suggestion is greatly appreciated!</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt 
  from matplotlib import animation
  from matplotlib.animation import FuncAnimation
  import random
  
  x = 0
  y = 0
  
  x_data=[]
  y_data=[]
  
  fig, ax = plt.subplots()
  ax.set_xlim(-10,10)
  ax.set_ylim(-10,10)
  line, = ax.plot(0,0)
  
  def init():
      line.set_data([],[])
      return line,
  
  def move_random(s,t):
      direction = random.randint(1,4)
  
      if direction == 1:
          s += 1
      elif direction == 2:
          t += 1
      elif direction == 3:
          s+= -1
      elif direction == 4:
          t+= -1
  
  def animate_rw(i):
      move_random(x,y)
  
      x_data.append(x)
      y_data.append(y)
  
      line.set_xdata(x_data)
      line.set_ydata(y_data)
      return line,
  
  anim = animation.FuncAnimation(fig, animate_rw, init_func = init, frames = 200, interval = 10)
  plt.show()
  </code></pre>