title: How to refresh text in Matplotlib?
body: <p>I wrote this code to read data from an excel file and to plot them. For a certain x-value, I desire to know the y-values of all the lines so I create a slider to change this x-value but I'm not able to refresh the text which prints the y-value.</p>
  
  <p>The code is this</p>
  
  <pre><code>import numpy as np
  from openpyxl import load_workbook as ld
  import matplotlib
  matplotlib.use('TkAgg')
  import matplotlib.pyplot as plt
  from matplotlib.widgets import Slider
  
  wb = ld(filename='example.xlsx')
  data = wb['data']
  time = wb['time']
  row = data.max_row
  column = data.max_column
  x = np.ones((row, column))
  y = np.ones((row, column))
  result = np.ones(row)
  for i in range(0, row):
      for j in range(0, column):
  
          x[i][j] = time.cell(row=i+1, column=j+1).value
          y[i][j] = data.cell(row=i+1, column=j+1).value
  
  
  fig, ax = plt.subplots()
  plt.subplots_adjust(left=0.25, bottom=0.25)
  plt.plot(x[0], y[0], label='line1')
  plt.plot(x[1], y[1], label='line2')
  plt.plot(x[2], y[2], label='line3')
  line, = plt.plot((np.amin(x), np.amin(x)), (np.amin(y), np.amax(y)))
  plt.legend()
  plt.grid(True)
  
  
  axtime = plt.axes([0.25, 0.1, 0.65, 0.03])
  stime = Slider(axtime, 'time', np.amin(x), np.amax(x), valinit=np.amin(x))
  
  
  def y_text(r):
      ax.text(10, 8, str(r), style='italic')
  
  
  def find(t):
      global x, y, result
  
      for i in range(0, row):
          for j in range(0, column):
  
              if x[i][j] == t or (t &lt; x[i][j] and j == 0) or (t &gt; x[i][j] and j == column):
                  result[i] = y[i][j]
              elif x[i][j] &lt; t &lt; x[i][j+1]:
                  result[i] = ((t-x[i][j])/(x[i][j+1]-x[i][j]))*(y[i][j+1]-y[i][j])+y[i][j]
      return result
  
  
  def update(val):
      line.set_xdata(stime.val)
      find(stime.val)
      y_text(stime.val)
      fig.canvas.draw()
  stime.on_changed(update)
  
  
  plt.show()
  </code></pre>
  
  <p>and the result is this</p>
  
  <p><a href="https://i.stack.imgur.com/ZVRRP.png" rel="noreferrer"><img src="https://i.stack.imgur.com/ZVRRP.png" alt="enter image description here"></a></p>
  
  <p>As you can see the text is overwritten.</p>