title: How to assign values to an empty numpy array
body: <p>I want to know know if there is a way to assign value to a 2D numpy array</p>
  
  <pre><code>nbpas = 88
  nbtraj = 10000
  tst = np.empty((nbtraj, nbpas))
  print(tst)
  </code></pre>
  
  <p>Then I would like to assign a value of 50 on the axis 0 of this array so that each row would start by 50</p>
  
  <p>Can somebody help me with that</p>