Can you tell what a person is like from the people they date?

You cannot dictate ones personality by the people they date. One should not judge upon first sight, as well.

If the person is addicted to dating assholes or bitches, more than likely he or she is a pathologically rabid codependent.

I'm gonna say no. You will obviously get a first impression, but I wouldn't say you can tell what a person is like judging by the people they date. I feel like I am pretty good proof of that!

Nope, I've known people that were in a relationship but that had totally different personality's. From what i've noticed, people usually go for someone that has traits they lack, so usually more of an opposites attract sort of thing.

Well, a little bit. Those dates form data. A thoughtful analysis of that data will invariably tell you something about their pattern of behaviour, or at least increase the certainty with which you can make a claim about their behaviour.

I definitely don't think you could tell everything about a person though, or ever most of it. People are astonishingly complicated; we're the aggregate of countless generations of genetic material, years of societal conditioning and a lifetime of personal experiences. You can't learn much about a person from such a narrow source of data.

No!

You never know why someone chooses a particular person, and hell most people can't explain their reason themselves. I think you could certainly interpret parts of their personality by it, but you're still just guessing. A young woman could choose to date older men because she is materialistic, has daddy issues or because she is attracted to power or knowledge. You just never really know and if you know the person well enough you most likely understand why they make certain choices. That's a hell of a lot easier than studying the flaws and characteristics of all their romantic partners.

Who knows... it could be like, "Oh my god! We fit together perfectly! We're, like, the same person!" Or it could be, "Opposites attract... That's so true."