title: Python matplotlib histogram very slow
body: <p>I was trying to plot a histogram for the data from a .csv file. But when I run it, it is very very slow. I waited for like 20 minutes, but still cannot get the plot. May I ask that is the problem? </p>
  
  <p>The following lines are my code. </p>
  
  <pre><code>import pandas as pd
  import matplotlib.pyplot as plt
  
  spy = pd.read_csv( 'SPY.csv' )
  stock_price_spy = spy.values[ :, 5 ]
  
  n, bins, patches = plt.hist( stock_price_spy, 50 )
  plt.show()
  </code></pre>