It's a good idea to learn a language for each purpose, but I wouldn't worry about it all that much yet. Just focus on at least getting a language under your belt before taking on more. I've been using PHP for over a year before I went over to another language like Java.
Ludum Dare is next weekend if you want a little challenge at making a game in 48 hours which then gets scored by the community. :p For the preceding ones I've been using Game Maker and this will be my first time using Java!
You could even use this chance to make a game in HTML5 if you want to try learning it, it's a wise-choice and I'd totally go for it! Don't think there's things you need to know before making a game, I got into Java by skipping right into game development.
Just follow a tutorial or two
Don't worry, this is all for the future. I'm still on python.
Well, I'm not sure I'd want to go into HTML5 for game dev without actually knowing HTML5 in the first place. I feel like I wouldn't learn as much, especially if I plan on using HTML5 for things other than games.
Still, it's a possibility, so thanks for the suggestion.
NINJA EDIT: If I don't try HTML5, I'll just use PyGame and see if I can get it working. I was playing around with Pyglet as well which could also work.