我可以使用python下载网页的源代码吗？

import urllib2
def download(url, num_retries = 5):
    '''
    function: 下载网页源代码，如果遇到 5xx 错误状态，则继续尝试下载，直到下载 num_retries 次为止。
    '''
    print "downloading " , url
    try:
        html = urllib2.urlopen(url).read()
    except urllib2.URLError as e:
        print "download error: " , e.reason
        html = None
        if num_retries > 0:
            if hasattr(e,'code') and 500 <= e.code < 600:
                return download(url, num_retries-1)

    return html