urllib.py 文件源码

def redirect_internal(self, url, fp, errcode, errmsg, headers, data):
        if 'location' in headers:
            newurl = headers['location']
        elif 'uri' in headers:
            newurl = headers['uri']
        else:
            return
        fp.close()
        # In case the server sent a relative URL, join with original:
        newurl = basejoin(self.type + ":" + url, newurl)

        # For security reasons we do not allow redirects to protocols
        # other than HTTP, HTTPS or FTP.
        newurl_lower = newurl.lower()
        if not (newurl_lower.startswith('http://') or
                newurl_lower.startswith('https://') or
                newurl_lower.startswith('ftp://')):
            raise IOError('redirect error', errcode,
                          errmsg + " - Redirection to url '%s' is not allowed" %
                          newurl,
                          headers)

        return self.open(newurl)