because it's more fun than doing my reading

I have to read this whole chapter on reptiles even though the class is on mammals, birds and turtles, only one of which is a reptile. So I'm skimming the non-turtle parts. But the snake part got me thinking about what Nagini might look like. I figured she was a viper but the size of a python. One of the biggest vipers is the Gabon viper. 174cm is pretty big. And check this out:
Following a strike, they tend to hold on to their prey until it is dead. Prey is also lifted off of the ground to prevent it getting hold of anything. Anything large enough to pose more of a threat is released and searched for after a few minutes.

That sounds like her to me.

Except I think ( DH spoilers )