YoutubeIE: reuse instances of InfoExtractors (closes #998)

When a IE is added to the list, it's also added to a dictionary. When a IE is requested it first looks in the dictionary and if there's no instance it will create a new one.

That way _real_initialize is only called once for each IE, saving time if it needs to login for example.

youtube_dl/YoutubeDL.py

@@ -97,6 +97,7 @@ class YoutubeDL(object):
     def __init__(self, params):
         """Create a FileDownloader object with the given options."""
         self._ies = []
+        self._ies_instances = {}
         self._pps = []
         self._progress_hooks = []
         self._download_retcode = 0
@@ -111,8 +112,21 @@ def __init__(self, params):
     def add_info_extractor(self, ie):
         """Add an InfoExtractor object to the end of the list."""
         self._ies.append(ie)
+        self._ies_instances[ie.ie_key()] = ie
         ie.set_downloader(self)
 
+    def get_info_extractor(self, ie_key):
+        """
+        Get an instance of an IE with name ie_key, it will try to get one from
+        the _ies list, if there's no instance it will create a new one and add
+        it to the extractor list.
+        """
+        ie = self._ies_instances.get(ie_key)
+        if ie is None:
+            ie = get_info_extractor(ie_key)()
+            self.add_info_extractor(ie)
+        return ie
+
     def add_default_info_extractors(self):
         """
         Add the InfoExtractors returned by gen_extractors to the end of the list
@@ -294,9 +308,7 @@ def extract_info(self, url, download=True, ie_key=None, extra_info={}):
          '''
         
         if ie_key:
-            ie = get_info_extractor(ie_key)()
-            ie.set_downloader(self)
-            ies = [ie]
+            ies = [self.get_info_extractor(ie_key)]
         else:
             ies = self._ies
 

youtube_dl/extractor/common.py

@@ -106,6 +106,11 @@ def _real_extract(self, url):
         """Real extraction process. Redefine in subclasses."""
         pass
 
+    @classmethod
+    def ie_key(cls):
+        """A string for getting the InfoExtractor with get_info_extractor"""
+        return cls.__name__[:-2]
+
     @property
     def IE_NAME(self):
         return type(self).__name__[:-2]