title: matplotlib.widgets.Slider with histogram
body: <p>I'm trying to make the interactive histogram but during</p>
  
  <p>update old histogram is not been cleared, as shown in the image below.</p>
  
  <p><a href="https://i.stack.imgur.com/kr3V0.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/kr3V0.png" alt="enter image description here"></a>)</p>
  
  <p>above plot is generated using following code</p>
  
  <pre class="lang-python prettyprint-override"><code>from functools import lru_cache
  import scipy.stats as ss
  import matplotlib.pyplot as plt
  import matplotlib.widgets as widgets
  
  fig, ax = plt.subplots()
  plt.subplots_adjust(bottom=0.25)
  
  weight = ss.lognorm(0.23, 0, 70.8)
  
  @lru_cache
  def sampling(n):
      return [ weight.rvs().mean() for i in range(1000) ]
  
  theme = {
      'color' : "#1f77b4",
      'alpha' : 0.7,
  }
  
  t = ax.hist(sampling(100), **theme)
  
  slider = widgets.Slider(
      ax      = plt.axes([0.25, 0.1, 0.5, 0.03]),
      label   = "n",
      valmin  = 10,
      valmax  = 1000,
      valinit = 100,
      valstep = 1
  
  def update(val):
      global t
      del t
      t = ax.hist(sampling(int(val)), **theme)
      fig.canvas.draw_idle()
  
  slider.on_changed(update)
  ax.set_title('Distribution of Sample Size Mean')
  plt.show()
  </code></pre>