title: Python3: Variable Assignment, Underscore in Name produces weird Behavior in Pycharm
body: <p>The following weird behavior I experienced in Python 3.5 using Pycharm in debug mode, but only if I <code>import numpy</code>.</p>
  
  <p>There are two variables <code>importance</code> and <code>importance_stack</code>. 
  When I assign the values of <code>importance</code> to <code>importance_stack</code> something weird happens. The value of <code>importance_stack</code> is not the expected <code>[1,1,1,1,1]</code> but <code>[[1 1 1 1 1]\n[1 1 1 1 1]\n[1 1 1 1 1]]</code></p>
  
  <pre><code>import numpy as np
  importance_stack = []
  importance = [1,1,1,1,1]
  importance_stack[:] = importance
  </code></pre>
  
  <p>By chance I found out, that when I rename <code>importace_stack</code> to for instance <code>iss</code> it behaves as expected, also if I do not import numpy.</p>
  
  <pre><code>iss=[]
  importance = [1,1,1,1,1]
  iss[:] = importance
  </code></pre>
  
  <p>Can somebody explain to me why that happens? Or am I messing something up in my understanding?
  Thanks a lot!</p>
  
  <p>edit:
  - screenshot attached
  <a href="https://i.stack.imgur.com/owvn1.png" rel="nofollow noreferrer">screenshot</a></p>