What the article means is that a single Python OS process can have multiple OS threads but only one of them can execute Python bytecode at any given time. So if

What the article means is that a single Python OS process can have multiple OS threads but only one of them can execute Python bytecode at any given time. So if you have a multithreaded Python application (on CPython), only one of those threads will run your code at a time while the others are waiting. Naturally you can have multiple OS processes of Python that run in parallel. This is how Python web services usually work. Then, of course, you need to share memory explicitly via some mechanism like Redis or SysV shared memory, so it leads to different design considerations.