How to modify my code to get every word & previos word from file?please help

# a look at the Tkinter Text widget

# use ctrl+c to copy, ctrl+x to cut selected text,

# ctrl+v to paste, and ctrl+/ to select all
  # count words in a text and show the first ten items
 # by decreasing frequency

import Tkinter as tk
import os, glob
import sys
import string
import re
import tkFileDialog      
def most_frequant_word():    
 browser= tkFileDialog.askdirectory()
 #browser= os.listdir(a)

 word_freq = {}
 for root, dirs, files in os.walk(browser):
    #print 'Looking into %s' % root.split('\\')[-1]
    #print 'Found %d dirs and %d files' % (len(dirs), len(files))
    text1.insert(tk.INSERT, 'Found %d dirs and %d files' % (len(dirs), len(files)))
    text1.insert(tk.INSERT, "\n")
    for idx, file in enumerate(files):
     
     print 'File #%d: %s' % (idx + 1, file)
       #text1.insert(tk.INSERT, 'File #%d: %s' % (idx + 1, file))
       #text1.insert(tk.INSERT, "\n")
     ff = open (os.path.join(root, file), "r")
     text = ff.read ( )
     ff.close ( )
     #word_freq = {}     
     word_list = text.split()
     for word in word_list:
      word = word.lower()
      word = word.rstrip('.,/"\ -_;\[](){} ')

      #if word.isalpha():
                # build the dictionary
      count = word_freq.get(word, 0)
      word_freq[word] = count + 1
 
       # create a list of (freq, word) tuples
      freq_list = [(word,freq ) for freq,word  in word_freq.items()]
     
       # sort the list by the first element in each tuple (default)
      freq_list.sort(reverse=True)
     
     for n, tup in enumerate(freq_list):
    # print the first ten items
      if n < 5:
       if idx == 3:  
        print "%s times: %s" % tup
        text1.insert(tk.INSERT, "%s times: %s" % tup)
       #text1.insert(tk.INSERT, word)
        text1.insert(tk.INSERT, "\n")
        
# raw_input('\nHit enter to exit')
 
root = tk.Tk(className = " most_frequant_word")
# text entry field, width=width chars, height=lines text
v1 = tk.StringVar()
text1 = tk.Text(root, width=50, height=50, bg='green')
text1.pack()
# function listed in command will be executed on button click
button1 = tk.Button(root, text='Brows', command=most_frequant_word)
button1.pack(pady=5)
text1.focus()
root.mainloop()