Printing to a file via Python -

hopefully easy fix. i'm trying edit 1 field of file use import, when run following code leaves file blank , 0kb. advise i'm doing wrong?

import re #import regex can use commands  name = raw_input("enter filename:") #prompt file name, press enter open test.nhi if len(name) < 1 : name = "test.nhi" count = 0 fhand = open(name, 'w+') line in fhand:    words = line.split(',') #obtain individual words using split    words[34] = re.sub(r'\d', "", words[34]) #remove non-numeric chars string using regex    if len(words[34]) < 1 : continue # if 34th field blank go next line   elif len(words[34]) == 2 : "{0:0>3}".format([words[34]]) #add leading zeroes depending on length of field   elif len(words[34]) == 3 : "{0:0>2}".format([words[34]])   elif len(words[34]) == 4 : "{0:0>1}".format([words[34]])   fhand.write(words) #write line fhand.close() # close file after loop ends 

i have taken below text in 'a.txt' input , modified code. please check if it's work you.

#intial content of a.txt this,program,is,java,program this,program,is,12python,programs 

modified code follow:

import re   #reading file , updating values fhand = open('a.txt', 'r') tmp_list=[] line in fhand:   #split line using ','     words = line.split(',')    #remove non-numeric chars 34th string using regex     words[3] = re.sub(r'\d', "", words[3])   #update 3rd string     # if 3rd field blank go next line     if len(words[3]) < 1 :         #removed continue here need reconstruct original line , write file         print "field empty.continue..."      elif len(words[3]) >= 1 , len(words[3]) < 5 :        #format won't add leading zeros. zfill(5) add required number of leading zeros depending on length of word[3].         words[3]=words[3].zfill(5)      #after updating 3rd value in words list, again creating line out of it.     tmp_str = ",".join(words)     tmp_list.append(tmp_str) fhand.close()  #writing same file whand = open("a.txt",'w') val in tmp_list:     whand.write(val) whand.close() 

file content after running code

this,program,is,,program this,program,is,00012,programs