title: Looping through multiple Excel file to modify and rewrite original using pandas
body: <p>I'm new to this so please bear with me....
  I have an .xls file with 49 rows and 5 columns viz. a,b,c,d,e. I want to calculate the squareroot of (b^2+c^2+d^2) and put into the new column as f. in the same .xls file.
  Now imagine i have 49 of these files.
  I'm trying to write a code using pandas that automatically parse each and every file in the folder and add a column in the original file with the above formula.</p>
  <p>My code is :</p>
  <pre><code>import glob
  import pandas as pd
  import numpy as np
  #size = len(glob.glob('test/*.xls'))
  file = glob.glob('test/*.xls')
  for f in file:
      print(f)
      name = 12
      df = pd.read_excel(f, header = None)
      df.columns = ['a','b', 'c', 'd', 'e','f']
      df['Result'] = ((df['b']**2)+(df['c']**2)+(df['d']**2))**(1/2)
      df.to_excel(r'test/Nodal pressure at 8 us_at_Y_'+str(name)+'.5.xls', index = False)
      name = name + 1
  </code></pre>
  <p>I don't know if it is possible or not but anyhelp would be useful. Also, i'm new to the coding so i may not some basic.</p>