title: Matplotlib: plot the entire column values in pandas
body: <p>I have the following data frame <code>my_df</code>:</p>
  
  <pre><code>        my_1     my_2     my_3
  --------------------------------
  0         5       7        4
  1         3       5       13
  2         1       2        8
  3        12       9        9
  4         6       1        2
  </code></pre>
  
  <p>I want to make a plot where x-axis is categorical values with my_1, my_2, and my_3. y-axis is integer. For each column in <code>my_df</code>, I want to plot all its 5 values at x = my_i. What kind of plot should I use in matplotlib? Thanks!</p>