python-3.x - Is there a way to pull one file at a time in a function, run it through another function, and then pull the next file?

Question

Here's the gist of what I'm trying to do:

I'm performing FFTs on multiple files from a directory.

I want to write a function that pulls the first file from the directory, runs it through a FFT function (which will call the file-pull function), then pull the next file from the directory.

So the question is how to write a function that saves my place from the previous call and pulls the next subsequent file from the directory.

Thanks in advance!