python脚本： 双向统计文件字符、单词数、行数

#!/usr/bin/python

import sys
import os

if len(sys.argv) == 1:
data = sys.stdin.read()
else:
try:
fn = sys.argv[1]
except IndexError:
print "please follow a argument at %s" %__file__
sys.exit()

if not os.path.exists(fn):
print "%s is not exits." %fn
sys.exit()

fd = open(sys.argv[1])
data = fd.read()

chars = len(data)
words = len(data.split())
lines = data.count('\n')

print "%(lines)s %(words)s %(chars)s" %locals()