python urllib模块显示下载进度

python的urllib模块显示下载进度.

def report_hook(count, block_size, total_size):
...     print '%02d%%'%(100.0 * count * block_size/ total_size)
... 
urllib.urlretrieve("http://www.jbxue.com/", reporthook= report_hook)
00%
01%
03%
...