Delay initialization of InfoExtractors until they are needed

youtube_dl/extractor/__init__.py

@@ -997,11 +997,18 @@ _ALL_CLASSES = [
 _ALL_CLASSES.append(GenericIE)
 
 
+def gen_extractor_classes():
+    """ Return a list of supported extractors.
+    The order does matter; the first extractor matched is the one handling the URL.
+    """
+    return _ALL_CLASSES
+
+
 def gen_extractors():
     """ Return a list of an instance of every supported extractor.
     The order does matter; the first extractor matched is the one handling the URL.
     """
-    return [klass() for klass in _ALL_CLASSES]
+    return [klass() for klass in gen_extractor_classes()]
 
 
 def list_extractors(age_limit):