title: Python numpy unwrap function
body: <p>I am hoping to convert a array of radians into range <code>[0, 2*pi)</code> and <a href="https://docs.scipy.org/doc/numpy/reference/generated/numpy.unwrap.html" rel="noreferrer">numpy unwrap</a> function is exactly what I need  </p>
  
  <p>However, when I run the following code to input <code>a = [pi, 2*pi, 3*pi]</code>: </p>
  
  <pre><code>import numpy as np
  
  a = np.array([np.pi, 2*np.pi, 3*np.pi])
  np.unwrap(a)
  </code></pre>
  
  <p>I expect the results to be close to <code>[pi, 0, pi]</code>. However, the output is still:</p>
  
  <pre><code>array([ 3.14159265,  6.28318531,  9.42477796])
  </code></pre>
  
  <p>It is not unwrapped. However, if I instead run the following without using the <code>numpy.pi</code></p>
  
  <pre><code>a = np.array([3.14159265,  6.28318531,  9.42477796])
  np.unwrap(a)
  </code></pre>
  
  <p>The output is correct:</p>
  
  <pre><code>array([  3.14159265e+00,   2.82041412e-09,   3.14159265e+00])
  </code></pre>
  
  <p>what is going on?</p>