title: How does numpy determine the array data type when it contains multiple dtypes?
body: <p>I am trying to do hands on the numpy, i cam across following datatype when 
  used inbuilt method dtype.Following the few results i have got.
  Can you please explain what it means by u11</p>
  
  <pre><code>a1 = np.array([3,5,'p'])
  print(a1.dtype)
  </code></pre>
  
  <p>o/p = >U11</p>