What approaches are used for data transfer between processes in Python's multiprocessing module?

The Python multiprocessing module uses several main approaches for data transfer between processes:

1. Queues (Queue) — thread-safe data structures that allow processes to exchange objects via put() and get() methods. Under the hood, the queue uses IPC (inter-process communication) mechanisms.

2. Pipes (Pipe) — bidirectional communication channels between two processes, enabling data transfer in both directions.

3. Shared objects via Manager — a special server process that manages shared objects (lists, dictionaries, etc.) accessible to multiple processes.

4. Shared memory (shared_memory) — starting from Python 3.8, the module provides the ability to create shared memory blocks that can be used by different processes for data exchange without serialization.

Example of using a queue:

from multiprocessing import Process, Queue

def worker(q):
    q.put('Hello from child process')

if __name__ == '__main__':
    q = Queue()
    p = Process(target=worker, args=(q,))
    p.start()
    print(q.get())  # Receive message from child process
    p.join()