title: Add Uneven Sized Data Columns in Pandas
body: <p>I want to add a list as a column to the df dataframe. The list has a different size than the column length.</p>
  
  <pre><code>df = 
  A   B   C
  1   2   3
  5   6   9
  4   
  6       6
  8       4
  2       3
  4   
  6       6
  8       4
  
  
  D = [11,17,18]
  </code></pre>
  
  <p>I want the following output</p>
  
  <pre><code>df = 
  A   B   C   D
  1   2   3   11
  5   6   9   17
  4           18
  6       6
  8       4
  2       3
  4   
  6       6
  8       4
  </code></pre>
  
  <p>I am doing the following to extend the list to the size of the dataframe by adding "nan"</p>
  
  <pre><code># number of nan value require for the list to match the size of the column
  extend_length = df.shape[0]-len(D)
  
  # extend the list 
  D.extend(extend_length * ['nan'])
  
  # add to the dataframe
  df["D"] = D
  
  A   B   C   D
  1   2   3   11
  5   6   9   17
  4           18
  6       6   nan
  8       4   nan
  2       3   nan
  4           nan
  6       6   nan
  8       4   nan
  </code></pre>
  
  <p>Where "nan" is treated like string but I want it to be empty ot "nan", thus, if I search for number of valid cell in D column it will provide output of 3.</p>