python efficiently repeats sample code that supports GB level large files

This is as follows:

#coding=utf-8
 
import sys, re, os
 
def getDictList(dict):
  regx = '''[\w\~`\!\@\#\$\%\^\&\*\(\)\_\-\+\=\[\]\{\}\:\;\,\.\/\<\>\?]+'''
  with open(dict) as f:
    data = f.read()
    return re.findall(regx, data)
 
def rmdp(dictList):
  return list(set(dictList))
 
def fileSave(dictRmdp, out):
  with open(out, 'a') as f:
    for line in dictRmdp:
      f.write(line + '\n')
 
def main():
  try:
    dict = sys.argv[1].strip()
    out = sys.argv[2].strip()
  except Exception, e:
    print 'error:', e
    me = os.path.basename(__file__)
    print 'usage: %s <input> <output>' %me
    print 'example: %s dict.txt dict_rmdp.txt' %me
    exit()
 
  dictList = getDictList(dict)
  dictRmdp = rmdp(dictList)
  fileSave(dictRmdp, out)
   
if __name__ == '__main__':
  main()