title: Single column dataframe containing 1D lists using a numpy 2D array
body: <p>I want to create a new single column pandas dataframe using a 2D numpy array. Apparently, each row should contain 1D lists. Following is a simplified reproducible example.</p>
  
  <pre><code>import pandas as pd
  import numpy as np
  
  arr = np.ones((4,3)) # could be any 2D array
  </code></pre>
  
  <p>What I want is,</p>
  
  <pre><code>       lists
  0  [1, 1, 1]
  1  [1, 1, 1]
  2  [1, 1, 1]
  3  [1, 1, 1]
  </code></pre>
  
  <p>Now, <code>df  = pd.DataFrame(arr, columns=['lists'])</code> gives the error,</p>
  
  <pre><code>ValueError: Shape of passed values is (4, 3), indices imply (4, 1)
  </code></pre>
  
  <p>And <code>df = pd.DataFrame(list(arr), columns=['lists'])</code> gives the error, </p>
  
  <pre><code>ValueError: 1 columns passed, passed data had 3 columns
  </code></pre>
  
  <p>Finally, <code>df = pd.DataFrame(arr.flatten(), columns=['lists'])</code> gives a wrong dataframe with all cells having a scalar <code>1</code>.</p>
  
  <p>How do I get what I want?</p>