Multithreading versus multiprocessing

Now that we have come to the end of our discussion on multi-processing, it is a good time to compare and contrast the scenarios where one needs to choose between scaling using threads in a single process or using multiple processes in Python.

Here are some guidelines.

Use multithreading in the following cases:

1. The program needs to maintain a lot of shared states, especially mutable ones. A lot of the standard data structures in Python, such as lists, dictionaries, and others, are thread-safe, so it costs much less to maintain a mutable shared state using threads than via processes.

2. The program needs to keep a low memory foot-print.

3. The program spends a lot of time doing I/O. Since the GIL is released by threads doing I/O, it doesn't affect the time taken by the threads to perform I/O.

4. The program doesn't have a lot of data parallel operations which it can scale across multiple processes

Use multiprocessing in these scenarios:

1. The program performs a lot of CPU...