title: Matplotlib - How to make the marker face color transparent without making the line transparent
body: <p>I know how to set the transparency of a line in matplotlib. For example, the following code makes the line and the markers transparent.</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  
  vec = np.random.uniform(0, 10, 50)
  f = plt.figure(1)
  ax = f.add_subplot(111)
  ax.plot(vec, color='#999999', marker='s', alpha=0.5)
  </code></pre>
  
  <p>I want line's alpha=1.0, and marker's face color to be semi-transparent (alpha=0.5). Can this be done in matplotlib? </p>
  
  <p>Thank you.</p>