Python's support for multithreaded programs has improved considerably over the last few years with the advent of the "free-threaded" version of the language. But testing multithreaded programs is notoriously difficult, because the underlying host system determines the thread-execution ordering, which adds an element of non-determinism. At PyCon US, Larry Hastings gave a talk (YouTube video) about his blanket project, which is meant to provide mechanisms for deterministic testing of multithreaded Python code.