python运行问题
import sys

def readfile(filename):
'''Print a file to the standard output.'''
f = open(filename)
while True:
line = f.readline()
if len(line) == 0:
break
print (line), # notice comma
f.close()

# Script starts from here
if len(sys.argv) < 2:
print ('No action specified.')
sys.exit

if sys.argv[1].startswith('--'):
option = sys.argv[1][2:]
# fetch sys.argv[1] but without the first two characters
if option == 'version':
print ('Version 1.2')
elif option == 'help':
print ('''\
This program prints files to the standard output.
Any number of files can be specified.
Options include:
--version : Prints the version number
--help : Display this help''')
else:
print ('Unknown option.')
sys.exit
else:
for filename in sys.argv[1:]:
readfile(filename)


问题：
No action specified.
Traceback (most recent call last):
File "C:/Documents and Settings/Administrator/桌面/python test/cat.py", line 18, in <module>
if sys.argv[1].startswith('--'):
IndexError: list index out of range

[解决办法]
lz 显然没有在执行程序的时候，提供一个（命令行）参数
[解决办法]
sys.argv[1]:越界