测试一下

import os
import sys
import urllib
from time import time, sleep

class RateLimit(object):
"""Rate limit a url fetch"""
def __init__(self, rate_limit):
"""rate limit in kBytes / second"""
self.rate_limit = rate_limit
self.start = time()
def __call__(self, block_count, block_size, total_size):
total_kb = total_size / 1024
downloaded_kb = (block_count * block_size) / 1024
elapsed_time = time() - self.start
if elapsed_time != 0:
#实际下载速度
rate = downloaded_kb / elapsed_time
print "%d kb of %d kb downloaded %f.1 kBytes/s\n" % (downloaded_kb ,total_kb, rate),
expected_time = downloaded_kb / self.rate_limit
sleep_time = expected_time - elapsed_time
print "Sleep for", sleep_time
#等待时间
if sleep_time > 0:
sleep(sleep_time)