import commands, os

def file_exists(fichier):
   try:
      file(fichier)
      return True
   except:
      return False

commands.getoutput('wget http://www.lechuck.org/ifup')
Ifup = file_exists(ifup)

---

iziBook:~/prog/python philemon$ python resetwifi.py 
Traceback (most recent call last):
  File "resetwifi.py", line 13, in ?
    Ifup = file_exists(ifup)
NameError: name 'ifup' is not defined