title: Plot hollow circles in plt.scatter
body: <p>I would like to plot a scatter plot by using 2 indexes [ChildrenHeight, ParentHeight] for a categorical variable: [gender]. However, I have tired many approaches to draw a empty circle with distinct edgecolors.  </p>
  
  <p>I have tried:</p>
  
  <pre><code>plt.scatter(X[:, 0], X[:, 1], c=y, marker = 'o',facecolors='none', cmap=plt.cm.Set1)
  </code></pre>
  
  <p>but it just gave me full circles:</p>
  
  <p><a href="https://i.stack.imgur.com/nNxwz.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/nNxwz.png" alt="enter image description here"></a></p>