title: Combine multiple csv files and add/average columns based on matching data
body: <p>I have a bunch of different csv files in a directory, the first column contains names, the second and third columns contain numbers. I would like to combine all of the rows with same names, and then average the value in the 2nd column and add the value in the 3rd.</p>
  <pre><code>example csv 1:
  
  John 5 5
  Mark 10 5
  Peter 20 5
  
  example csv 2:
  
  John 10 5
  Mark 20 5
  Peter 30 5
  
  Expected combined file:
  
  John 7.5 10
  Mark 15 10
  Peter 25 10
  </code></pre>
  <p>I have this so far, which combines all the files into one:</p>
  <pre><code>    os.chdir(r'\Pathtofiles')
      extension = 'csv'
      all_filenames = [i for i in glob.glob('*.{}'.format(extension))]
      combined_csv = pd.concat([pd.read_csv(f) for f in all_filenames ])
  
  I get this result:
  
  John 5 5
  Mark 10 5
  Peter 20 5
  John 10 5
  Mark 20 5
  Peter 30 5
  
  </code></pre>
  <p>but not sure how to get my expected result</p>