title: numpy array concatenate with extra column to each array
body: <p>I try to split a numPy array in roughly equal parts and merge them together with an extra value but end up being confused how I could do this. I have a list : [0., 2.25, 4., 4., 4., 4., 4., 4., 4., 2.25], which after an np.array_split and concatenate with an extra column should end up like: [0.  , 2.25, 4., 8., 4., 4., 4., 8., 4., 4., 8., 4.  , 2.25]</p>
  
  <p>The steps I took:</p>
  
  <pre><code>&gt;&gt;&gt; import numpy as np
  &gt;&gt;&gt; list = [0., 2.25, 4., 4., 4., 4., 4., 4., 4., 2.25]
  &gt;&gt;&gt; x = np.array(list)
  &gt;&gt;&gt; print(x)
  [0.   2.25 4.   4.   4.   4.   4.   4.   4.   2.25]
  &gt;&gt;&gt; x = np.array_split(list, 4)
  &gt;&gt;&gt; print(x)
  [array([0.  , 2.25, 4.  ]), array([4., 4., 4.]), array([4., 4.]), 
  array([4.  , 2.25])]
  &gt;&gt;&gt; x = np.concatenate([x, 8])
  Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
  ValueError: all the input arrays must have same number of dimensions
  </code></pre>
  
  <p>When I keep the array in the same shape, it will add it to the end of the list</p>
  
  <pre><code>&gt;&gt;&gt; x = np.concatenate([[x, y]])
  &gt;&gt;&gt; print(x)
  [list([array([0.  , 2.25, 4.  ]), array([4., 4., 4.]), array([4., 
  4.]), array([4.  , 2.25])])
   list([8])]
  </code></pre>
  
  <p>I understand that it might be more easy to do so, if you know the shape of the individual arrays and so you could add an extra column with the single value of 8 but array_split doesn't have equal sizes as seen above.</p>
  
  <p>Do I miss a step over here, is it even possible what I want to achieve?</p>