python接受命令选项-h

python在用命令行的时候能够接受很多参数，到底是如何接受那些参数和选项呢？

import sys, getopt

opts, args = getopt.getopt(sys.argv[1:], "hi:o:")

input_file=""

output_file=""

for op, value in opts:

    if op == "-i":

        input_file = value

    elif op == "-o":

        output_file = value

    elif op == "-h":

        usage()

        sys.exit()