urllib 如何限速下载

	 

	#!/usr/bin/python 

	#coding:utf-8

	 

	 

	""" 

	urllib 如何限速下载

	file:ratelimit-urllib.py

	Fetch a url rate limited 

	 

	Syntax: rate URL local_file_name 

	 

	python ratelimit-urllib.py 200 http://localhost/share/netbeans-7.0-ml-linux.sh  1.sh

	 

	""" 

	 

	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: 

	            #实际易做图

	            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) 

	 

	def main(): 

	    """Fetch the contents of urls""" 

	    if len(sys.argv) != 4: 

	        print 'Syntax: %s "rate in kBytes/s" URL "local output path"' % sys.argv[0] 

	        raise SystemExit(1) 

	    rate_limit, url, out_path = sys.argv[1:] 

	    rate_limit = float(rate_limit) 

	    print "Fetching %r to %r with rate limit %.1f" % (url, out_path, rate_limit) 

	    #这个扩展接口支持一个回调函数，每下载一段就调用一次回调函数

	    urllib.urlretrieve(url, out_path, reporthook=RateLimit(rate_limit)) 

	 

	if __name__ == "__main__": main()   

补充：Web开发 , Python ,

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