title: Pandas copy column names from one dataframe to another
body: <p>Let's say that we have two pandas data frames. The first one hasn't got column names:</p>
  
  <pre><code>no_col_names_df = pd.DataFrame(np.array([[1,2,3], [4,5,6], [7,8,9]]))
  </code></pre>
  
  <p>The second has:</p>
  
  <pre><code>col_names_df = pd.DataFrame(np.array([[10,2,3], [4,45,6], [7,18,9]]),
                             columns=['col1', 'col2', 'col3'])
  </code></pre>
  
  <p>What I want to do is to get copy column <em>names</em> from the <code>col_names_df</code> to <code>no_col_names_df</code> so that the following data frame is created:</p>
  
  <pre><code>    col1    col2    col3
  0   1       2       3
  1   4       5       6
  2   7       8       9
  </code></pre>
  
  <p>I've tried the following:</p>
  
  <pre><code>new_df_with_col_names = pd.DataFrame(data=no_col_names_df, columns=col_names_df.columns)
  </code></pre>
  
  <p>but instead of values from the <code>no_col_names_df</code> I get <code>NaN</code>s.</p>