new_contents: """Compute mean volume"""
  
  import pandas as pd
  
  def get_mean_volume(symbol):
      """Return the mean volume for stock indicated by symbol.
      
      Note: Data for a stock is stored in file: data/<symbol>.csv
      """
      df = pd.read_csv("data/{}.csv".format(symbol))  # read in data
      #Compute and return the mean volume for this stock
      return df.Volume.mean()
  
  def test_run():
      """Function called by Test Run."""
      for symbol in ['AAPL', 'IBM']:
          print "Mean Volume"
          print symbol, get_mean_volume(symbol)
  
  
  if __name__ == "__main__":
      test_run()
  
subject: Create mean_vol.py