title: Concatenate all rows of a numpy matrix in python
body: <p>I have a numpy matrix and would like to concatenate all of the rows together so I end up with one long array.</p>
  
  <pre><code>#example
  
  input:
  [[1 2 3]
   [4 5 6}
   [7 8 9]]
  
  output:
  [[1 2 3 4 5 6 7 8 9]]
  </code></pre>
  
  <p>The way I am doing it now doe not seem pythonic.  I'm sure there is a better way.</p>
  
  <pre><code>combined_x = x[0] 
  for index, row in enumerate(x):
      if index!= 0:
          combined_x = np.concatenate((combined_x,x[index]),axis=1)
  </code></pre>
  
  <p>Thank you for the help.</p>