rg3/youtube-dl — pull request #1007 by jaimeMF (2013-07-08 13:15:12+00:00)
Title: 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.