title: Can numpy einsum() perform outer addition?
body: <p>In numpy, we can perform "outer addition" between two vectors <code>a</code> and <code>b</code> like this:</p>
  
  <pre><code>a=np.c_[1,2,3]
  b=np.c_[4,5,6]
  result=a+b.T # alternatively this can be a.T+b
  </code></pre>
  
  <p>Is it possible to use <code>einsum</code> to make the same calculation? Any other fast alternatives? How about if <code>a</code> equals <code>b</code>?</p>