[common] Add new helper function _match_id

2 files changed, 9 insertions, 2 deletions

diff --git a/youtube_dl/extractor/abc.py b/youtube_dl/extractor/abc.py
index 7d89f44ee..69f89320c 100644
--- a/youtube_dl/extractor/abc.py
+++ b/youtube_dl/extractor/abc.py
@@ -22,8 +22,7 @@ class ABCIE(InfoExtractor):
     }
 
     def _real_extract(self, url):
-        mobj = re.match(self._VALID_URL, url)
-        video_id = mobj.group('id')
+        video_id = self._match_id(url)
         webpage = self._download_webpage(url, video_id)
 
         urls_info_json = self._search_regex(
diff --git a/youtube_dl/extractor/common.py b/youtube_dl/extractor/common.py
index 403791e6b..8d6a6f601 100644
--- a/youtube_dl/extractor/common.py
+++ b/youtube_dl/extractor/common.py
@@ -166,6 +166,14 @@ class InfoExtractor(object):
         return cls._VALID_URL_RE.match(url) is not None
 
     @classmethod
+    def _match_id(cls, url):
+        if '_VALID_URL_RE' not in cls.__dict__:
+            cls._VALID_URL_RE = re.compile(cls._VALID_URL)
+        m = cls._VALID_URL_RE.match(url)
+        assert m
+        return m.group('id')
+
+    @classmethod
     def working(cls):
         """Getter method for _WORKING."""
         return cls._WORKING