title: Python ValueError: could not convert string to float
body: <p>I have the code below, where the input is <code>h_ply =['0.12, 0.15, 0.2, 0.125']</code></p>
  <pre><code>h_ply = simpledialog.askstring('Laminate Properties','Ply Thickness')
  try:
      h_layer_list = [int(x) for x in h_ply.split(',')] 
      h_layer = np.array(h_layer_list) * 0.001 
  </code></pre>
  <p>I have also tried</p>
  <pre><code>h_ply1 = np.array(h_ply)
  h_layer = h_ply1.astype(np.float) 
  </code></pre>
  <p>But got the same error.</p>
  <p>I am trying to get <code>h_ply</code> list into a <code>np.array</code> of Floats. But a ValueError appears.
  I understand this could be because I should have <code>''</code> every number and not just at the ends? But ideally I want to avoid that to be more user friendly. What is the best way to get rid of this Error message?</p>
  <p>Thank you</p>