编写类du命令Python脚本

#!/usr/bin/env python
#_*_ coding:utf-8 _*_
#计算整个目录的大小,脚本接受-H参数，来加上适当的单位
#功能像du看齐

import os,sys
from optparse import OptionParser


def option():
        parser = OptionParser()
        parser.add_option('-H','--Human',dest='human',action='store_true',default=False,help='print sizes in human readable format')
        option,args = parser.parse_args()
        return option,args

def findfile(dirpath):
    path = os.walk(dirpath)
    for roots,dirs,files in path:
        for file in files:
                yield os.path.join(roots,file)


def filesize(option,file):
        size = os.path.getsize(file)
        if not option:
            return str(size)
        else:
            if size >= 1024000000:
                return str(size/1024/1024/1024) + 'G'
            elif size >= 1024000:
                return str(size/1024/1024) + 'M'
            elif size >= 4096:
                return str(size/1024) + 'K'
            else:
                return '4.0K'


def main():
        options,args = option()
        try:
                path = args[0]
        except IndexError as e:
                sys.exit('%s need a directory' % __file__)
        for file in findfile(path):
                size = filesize(options.human,file)
                print size,file


if __name__ == '__main__':
    main()