advanced_link_crawler.py 文件源码

def download(url, user_agent='wswp', num_retries=2, charset='utf-8', proxy=None):
    """ Download a given URL and return the page content
        args:
            url (str): URL
        kwargs:
            user_agent (str): user agent (default: wswp)
            charset (str): charset if website does not include one in headers
            proxy (str): proxy url, ex 'http://IP' (default: None)
            num_retries (int): number of retries if a 5xx error is seen (default: 2)
    """
    print('Downloading:', url)
    request = urllib.request.Request(url)
    request.add_header('User-agent', user_agent)
    try:
        if proxy:
            proxy_support = urllib.request.ProxyHandler({'http': proxy})
            opener = urllib.request.build_opener(proxy_support)
            urllib.request.install_opener(opener)
        resp = urllib.request.urlopen(request)
        cs = resp.headers.get_content_charset()
        if not cs:
            cs = charset
        html = resp.read().decode(cs)
    except (URLError, HTTPError, ContentTooShortError) as e:
        print('Download error:', e)
        html = None
        if num_retries > 0:
            if hasattr(e, 'code') and 500 <= e.code < 600:
                # recursively retry 5xx HTTP errors
                return download(url, num_retries - 1)
    return html