title: Python dataframe return column index of all max values as list
body: <p>I'm looking for the dataframe column with the greatest value, and assign this variable name to a new variable. One similar example <a href="https://stackoverflow.com/questions/23154821/how-to-find-out-which-variable-has-the-greatest-value">here</a> does not answer that in a dataframe setting. See the example below:</p>
  <pre><code>import pandas as pd
  
  data = {'A': [1, 2, 2, 0], 'B':[2, 0, 2, 1]}
  df = pd.DataFrame(data)
  </code></pre>
  <p>I'm looking to create a variable <code>df['C'] = [B, A, [A, B], B]</code>.</p>