title: Numpy array single value issue
body: <p>I was working on a problem where I ran into this issue.</p>
  
  <pre><code>import numpy as np
  str_format = "%H:%M:%S"
  
  a = 0    
  b = 0
  i = 0
  
  while(i &lt;= 238 ):  
  
      try:
          opening_time = data_dict['Open'][a]
          opening_time = datetime.strptime(opening_time, str_format)
          x = opening_time
  
          closing_time = data_dict['Close'][b]
          closing_time = datetime.strptime(closing_time, str_format)
          y = closing_time
  
          a = a + 1 
          b = b + 1
          i = i + 1
  
          s = [y - x]
  
          opening_duration_list = np.array(s)
          print(opening_duration_list)
  
      except ValueError:
  
          print("Variable opening Hours")
          a = a + 1 
          b = b + 1
          i = i + 1  
  </code></pre>
  
  <p>In this code I'm trying to have it so that each time the loop repeats <code>s = [Y - X]</code> it will create a new value in the numpy array. </p>
  
  <p>However, instead it's just created a single value with tonnes of rows. Does anyone have an idea on what I've messed up here and how I can fix it?</p>