You will want a scale that has a "tare" function if you don't want to have to do math every time. This means you can set a bowl or something on the scale, press a button, and it will reset to zero so that when you drop the snake in, the results are the actual weight of the snake rather than the weight of the snake plus the bowl.
We use a kitchen scale that we got at Walmart through the site-to-store thing. I had bought a different one first, but its tare function didn't work very well. When the weights for my animals made no sense, I tried it with food packages that are of course labeled with their weights. It was correct. I tried it with the same food packages using the tare function & the container I was using for the animals, and it was WAY off, so of course it went back to the store. So watch out for that.
Our corn will not sit still to be weighed, so we have to put her in a container with a lid.