title: Convert 2-D matrix into Dataframe in python
body: <pre><code>a = np.array([[5, 6, 7, 8],[5, 6, 7, 8]])
  
  df = pd.DataFrame(a, columns=['a'])
  </code></pre>
  
  <p>ValueError: Shape of passed values is (2, 4), indices imply (2, 1)</p>
  
  <p>I hope that the final result is:</p>
  
  <pre><code>a
  -----------
  [5, 6, 7, 8]
  [5, 6, 7, 8] 
  </code></pre>
  
  <p>Edit:</p>
  
  <pre><code>    df = pd.DataFrame({"a": [a]})
  
      a
  ----------------------------------
  0   [[5, 6, 7, 8], [5, 6, 7, 8]]
  </code></pre>
  
  <p>why?</p>