def _real_extract(self, url):
        mobj = re.match(self._VALID_URL, url)

        if mobj.group('course') and mobj.group('video'):  # A specific video
            course = mobj.group('course')
            video = mobj.group('video')
            info = {
                'id': course + '_' + video,
                'uploader': None,
                'upload_date': None,
            }

            baseUrl = 'http://openclassroom.stanford.edu/MainFolder/courses/' + course + '/videos/'
            xmlUrl = baseUrl + video + '.xml'
            mdoc = self._download_xml(xmlUrl, info['id'])
            try:
                info['title'] = mdoc.findall('./title')[0].text
                info['url'] = baseUrl + mdoc.findall('./videoFile')[0].text
            except __HOLE__:
                raise ExtractorError('Invalid metadata XML file')
            return info
        elif mobj.group('course'):  # A course page
            course = mobj.group('course')
            info = {
                'id': course,
                '_type': 'playlist',
                'uploader': None,
                'upload_date': None,
            }

            coursepage = self._download_webpage(
                url, info['id'],
                note='Downloading course info page',
                errnote='Unable to download course info page')

            info['title'] = self._html_search_regex(
                r'<h1>([^<]+)</h1>', coursepage, 'title', default=info['id'])

            info['description'] = self._html_search_regex(
                r'(?s)<description>([^<]+)</description>',
                coursepage, 'description', fatal=False)

            links = orderedSet(re.findall('<a href="(VideoPage.php\?[^"]+)">', coursepage))
            info['entries'] = [self.url_result(
                'http://openclassroom.stanford.edu/MainFolder/%s' % unescapeHTML(l)
            ) for l in links]
            return info
        else:  # Root page
            info = {
                'id': 'Stanford OpenClassroom',
                '_type': 'playlist',
                'uploader': None,
                'upload_date': None,
            }
            info['title'] = info['id']

            rootURL = 'http://openclassroom.stanford.edu/MainFolder/HomePage.php'
            rootpage = self._download_webpage(rootURL, info['id'],
                                              errnote='Unable to download course info page')

            links = orderedSet(re.findall('<a href="(CoursePage.php\?[^"]+)">', rootpage))
            info['entries'] = [self.url_result(
                'http://openclassroom.stanford.edu/MainFolder/%s' % unescapeHTML(l)
            ) for l in links]
            return info
dataset/ETHPy150Open yasoob/youtube-dl-GUI/youtube_dl/extractor/stanfordoc.py/StanfordOpenClassroomIE._real_extract