title: create new column based on condition in column of lists in pandas
body: <p>I have a dataframe containing column of lists:</p>
  <pre><code>col_1            
  [A, A, A, B, C]
  [D, B, C]
  [C]
  [A, A, A]
  NaN
  </code></pre>
  <p>I want to create new column, if the list starts with 3* <code>A</code> return 1, if not return 0:</p>
  <pre><code>col_1              new_col           
  [A, A, A, B, C]    1
  [D, B, C]          0
  [C]                0
  [A, A, A]          1
  NaN                0
  </code></pre>
  <p>I tried this but didn't work:</p>
  <pre><code>df['new_col'] = df.loc[df.col_1[0:3] == [A, A, A]]
  </code></pre>