I originally had "don't do that!" in my comment with your exact code, and edited it out for brevity because I've only seen a couple people do it (and they under

I originally had "don't do that!" in my comment with your exact code, and edited it out for brevity because I've only seen a couple people do it (and they understood the ramifications, which others have told you). If you're interested in brevity, this is as terse as it gets: L = [] if L is None else L