title: numexpr.evaluate("a+b",out=a)
body: <p>Is it safe in python numexpr to assign values to the same array you are operating on to avoid creating a temporary array?</p>
  
  <p>From the description of memory usage on the <a href="https://github.com/pydata/numexpr" rel="nofollow noreferrer">project homepage</a> it looks okay, but without diving into the source code, that is hardly a solid answer. </p>
  
  <p>I tried the following which works fine, but I am hoping for confirmation from someone more familiar with this package:</p>
  
  <pre><code>import numpy as np
  import numexpr as ne
  a = np.ones(5)
  b = a.copy()
  ne.evaluate("a+b",out=a)
  array([ 2.,  2.,  2.,  2.,  2.])
  </code></pre>