Multiprocessing with multiprocessing
Explore Python's multiprocessing module to overcome the Global Interpreter Lock limitations by running parallel processes. Understand how to spawn processes safely, manage workers using pools, and implement interprocess communication. This lesson enables you to optimize CPU-intensive tasks, balance memory and startup costs, and choose the right concurrency approach for your applications.
In the previous lesson, we examined a fundamental limitation of CPython: the Global Interpreter Lock (GIL). Threading works well for I/O-bound workloads, but it does not improve performance for CPU-bound tasks because only one thread can execute Python bytecode at a time. As a result, adding threads does not increase computational throughput for tasks such as image processing, numerical simulation, or large-scale data transformation.
To fully utilize multiple CPU cores, we must move beyond threads and beyond a single interpreter instance. Python’s approach to achieving true parallel execution is multiprocessing, spawning separate processes, each with its own Python interpreter and memory space. By distributing CPU-intensive work across multiple processes, we can execute tasks simultaneously and overcome the constraints imposed by the GIL.
Bypassing the GIL with processes
The multiprocessing module enables Python programs to spawn entirely new interpreter instances, each running in its own process. Unlike threads, which operate within a single process and share both memory and the Global Interpreter Lock (GIL), each process has an independent memory space and its own GIL.
Because processes are isolated from one another, they can execute truly in parallel on separate CPU cores. On a machine with eight cores, it is therefore possible (subject to workload and system limits) to run up to eight Python processes simultaneously at full computational capacity. The programming interface closely resembles that of threading.Thread. Instead of creating a Thread object, we create a Process object and provide a target function to execute. This design makes it ...