title: Fill array with rows of different lenghts Python
body: <p>So I found this:
  <a href="https://stackoverflow.com/questions/32037893/numpy-fix-array-with-rows-of-different-lengths-by-filling-the-empty-elements-wi">Numpy: Fix array with rows of different lengths by filling the empty elements with zeros</a></p>
  
  <p>But what I actually want is this:</p>
  
  <pre><code>mylist = [[1],[1,2],[1,2,3]]
  
  mylist.fill()
  &gt;&gt;&gt; [[0,0,1], [0,1,2], [1,2,3]]
  </code></pre>
  
  <p>I know that pandas' fillna fills but the 0 are at the right part of my matrix and I need them at the left part. Any clues?</p>