title: Apply function to a list of columns in a loop and output dataframe
body: <p>I have a function that is set up like this:</p>
  <pre><code>def function(df, apply_col, static_col):
      do something
      return df
  
  #calling the function
  df = function(df, 'col_a', 'st_col')
  </code></pre>
  <p>This works fine. But, I want to apply this function to a list of columns by name. I tried something like this:</p>
  <pre><code>col_list = ['col_a', 'col_b', 'col_c'....'col_n']
  
  for i in list:
      df = function(df, i, 'st_col')
  </code></pre>
  <p>I get a <code>TypeError: 'list' object is not callable</code></p>
  <p>I would like to apply this function to a dataframe in a loop with the static column staying the same and returning a resulting dataframe with all the columns having the function applied to them. Any ideas are appreciated!</p>