title: Collect values in cells into a list, then hold in a new dataframe using Pandas
body: <p>I have a dataframe that looks like this:  </p>
  
  <pre><code>| id   | col1 | col2 | col3 | col4 |
  |------|------|------|------|------|
  | 1    | A    | B    | C    | 0    |
  | 4    | X    | 0    | Y    | 0    |
  </code></pre>
  
  <p>I am trying to collect all the values in the rows into a list, and then put them into a new dataframe, like such:  </p>
  
  <pre><code>| id | output    |
  |----|-----------|
  | 1  | [A, B, C] |
  | 4  | [X, Y]    |  
  </code></pre>
  
  <p>I was trying to use an apply function to do this, but I can't seem to ignore the (string) <code>'0'</code> values.</p>
  
  <p>Here's the data:  </p>
  
  <pre><code>df = [    {'id' : 1, 'col1' : 'A', 'col2': 'B', 'col3':   'C', 'col4':'0'},
            {'id' : 4, 'col1' : 'X', 'col2':  '0', 'col3':  'Y', 'col4':'0'}
            ]
  df = pd.DataFrame(df)
  df = df[['col1', 'col2', 'col3', 'col4']]
  df
  </code></pre>