Threading vs. Multiprocessing: Differences and Use Cases

Multithreading and multiprocessing are two techniques for running portions of code concurrently in Python. While both share the goal of improving performance, there are distinct differences in their implementation and suitability for various tasks.

Core Concepts

• Threads: Created within a single process and share the same memory space.
• Processes: Isolated entities that have their own memory space and interact through interprocess communication (IPC).

Data Sharing

• Threads can access and modify shared data, while processes require explicit mechanisms for data exchange.

GIL (Global Interpreter Lock)

• Python's CPython interpreter has a GIL that prevents multiple threads from executing Python code simultaneously.
• This limitation can hinder parallel execution, especially in CPU-bound tasks.
• Processes are not subject to the GIL.

Resource Management

• Creating and destroying threads is cheaper and faster than processes.
• Processes can consume significant resources when used in large numbers or when communicating frequently.

When to Use Threads and Processes

• Threads: Suitable for tasks that:

  • Require real-time responsiveness (e.g., GUI event handling)
  • Do not involve heavy computation
  • Can easily share data

• Processes: Preferable for tasks that:

  • Are CPU-intensive
  • Have large memory requirements
  • Involve sensitive or isolated data
  • Are not time-critical

Queues for Parallel Execution

You can use queues (e.g., threading.Queue or multiprocessing.Queue) to manage a pool of jobs and limit the number of concurrently executed tasks:

# Create a queue
queue = multiprocessing.Queue()

# Initialize a process pool
pool = multiprocessing.Pool(4)

# Submit jobs to the pool
for job_argument in job_list:
    pool.apply_async(job, (job_argument,), callback=queue.put)

# Retrieve results from the queue
while not queue.empty():
    result = queue.get()
    # Process result...

Additional Resources

• [Multithreading vs. Multiprocessing in Python](https://realpython.com/python-multithreading/)
• [Using the Concurrent.futures Module in Python](https://realpython.com/concurrent-futures-in-python/)
• [Python Concurrency and Parallelism](https://www.coursera.org/specializations/python-concurrency-parallelism)