title: How do I drop every column that only contains values from a list pandas
body: <p>I want to be able to drop all columns that only have values from the list that I pass in.</p>
  <pre><code>list_of_drops = ['A','B']
  d ={'C1':['A','A','A','B','B','B'],
      'C2':['A','C','A','A','A','A'],
      'C3':['A','B','B','A','B','B'],
      'C4':['A','A','A','A','A','A'],
      'C5':['A','A','B','AC','A','B'],
      'C6':['A','A','AD','A','B','A']}
  
  df = pd.DataFrame (d, columns = ['C1','C2','C3','C4','C5','C6'])
  </code></pre>
  <p>In this example, I want to create a dataframe that only has C1, C3, and C4.</p>