title: Label data when doing a scatter plot in python
body: <p>I want to label every dot I plot in python, and I didn't find a proper way to do it.</p>
  
  <p>Assuming I have two lists of <code>n</code> elements called <code>a</code> and <code>b</code>, I print them this way :</p>
  
  <pre><code>    plt.figure()
      plt.grid()
      plt.plot(a , b , 'bo')
      plt.show()
  </code></pre>
  
  <p>I want to label every point with "Variable k" with <code>k</code> ranging from <code>1</code> to <code>n</code> obviously.
  Thanks for your time</p>