Trying to figure out how to save each frame of a played video game as an image

I have been researching and working on this for a while now, for my final project.

I originally was going to do something using imagemagick and combining pictures, but I really like compiling image frames together to make a movie like we've been doing with ffmpeg.

I found something that my seem to work...

NEVERMIND_ Half way through this I tried something new, and it's moved me a little farther than it did before,

a window pops up now, but then it disappears,

I started using i instead of self.framenum, because it kept throwing an error on that, the window then began to pop up but threw an error saying that i was referenced before it was defined, so i went through and fixed this, and now it is saying this for my variable name file, but no longer for i- so I am making progress...