title: Matplotlib graph with typical linestyle not showing
body: <p>I want a very simple plot:</p>
  
  <pre><code>import matplotlib.pyplot as plt
  import numpy as np
  
  for t in np.linspace(0,2*np.pi,100):
      plt.plot(np.cos(t), np.sin(t), color='blue', linestyle='-', linewidth=7)
  plt.show()
  </code></pre>
  
  <p>But nothing is appearing. I just get an empty plot. Where is my error?</p>