Well, PyCharm is already doing a lot of parsing for syntax highlighting and autocompletion and other goodies. They're checker implementation probably just takes

Well, PyCharm is already doing a lot of parsing for syntax highlighting and autocompletion and other goodies. They're checker implementation probably just takes the AST PyCharm already has available to it, which saves the round-trip of saving to a file and having an outside checker open and re-parse the file.