Python os.pipe vs multiprocessing.Pipe

Question

Recently I'm studying parallel programming tools in Python. And here are two major differences between os.pipe and multiprocessing.Pipe.(despite the occasion they are used)

1. os.pipe is unidirectional, multiprocessing.Pipe is bidirectional;
2. When putting things into pipe/receive things from pipe, os.pipe uses encode/decode, while multiprocessing.Pipe uses pickle/unpickle

I want to know if my understanding is correct, and is there other difference? Thank you.

Answer 1

I believe everything you've stated is correct.

On Linux, os.pipe is just a Python interface for accessing traditional POSIX pipes. On Windows, it's implemented using CreatePipe. When you call it, you get two ordinary file descriptors back. It's unidirectional, and you just write bytes to it on one end that get buffered by the kernel until someone reads from the other side. It's fairly low-level, at least by Python standards.

multiprocessing.Pipe objects are much more high level interface, implemented using multiprocessing.Connection objects. On Linux, these are actually built on top of POSIX sockets, rather than POSIX pipes. On Windows, they're built using the CreateNamedPipe API. As you noted, multiprocessing.Connection objects can send/receive any picklable object, and will automatically handle the pickling/unpickling process, rather than just dealing with bytes. They're capable of being both bidirectional and unidirectional.