title: meaning of comma operator in python
body: <p>I understood simple concepts about comma operator in python. For instance,</p>
  
  <pre><code>x0, sigma = 0, 0.1
  </code></pre>
  
  <p>means x0=0, and sigma=0.1. But I obtained a code that has a line that looks like the following. </p>
  
  <pre><code>y, xe = np.histogram(np.random.normal(x0, sigma, 1000))
  </code></pre>
  
  <p>where the output of y and xe are the followings.</p>
  
  <pre><code>y
  Out[10]: array([  3,  17,  58, 136, 216, 258, 189,  87,  31,   5], dtype=int64)
  
  xe
  Out[11]: 
  array([-0.33771565, -0.27400243, -0.21028922, -0.146576  , -0.08286279,
         -0.01914957,  0.04456364,  0.10827686,  0.17199007,  0.23570329,
          0.2994165 ])
  </code></pre>
  
  <p>I am not sure how to read y, xe expression. What could I look up to understand what it's saying?</p>