title: Matrix dot product in python
body: <p>I am new to python and confused on a code</p>
  
  <pre><code>X = np.array([2,3,4,4])
  print(np.dot(X,X))
  </code></pre>
  
  <p>This works</p>
  
  <pre><code>Y = np.array([[100],
          [200],
          [300],
          [400]])
  print(np.dot(Y,Y))
  </code></pre>
  
  <p>This doesn't. I understood it is because of the relationship with array dimensions. But I cant understand how. Please explain.</p>