Learning Objectives: After this lesson, you'll understand how to bypass the GIL with multiprocessing, use process pools efficiently, manage shared state safely, and implement inter-process communication patterns.
Why Multiprocessing?
Multiprocessing creates separate Python processes, each with its own GIL, enabling true parallelism.
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Multiprocessing vs Threading
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Basic Process Creation
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Process Pools
Process pools manage a fixed number of worker processes for efficient task distribution.
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Using Pool
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Pool Methods
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Shared State and Communication
Processes don't share memory by default. Here's how to share data.
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Shared Memory Values
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Manager for Complex Shared Objects
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Queues for Communication
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Pipes for Two-Way Communication
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Practical Patterns
Map-Reduce Pattern
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Parallel Pipeline
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Worker Pool with Callbacks
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Best Practices
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Key Takeaways
| Concept | Description |
|---|---|
| Process | Separate Python interpreter, own GIL |
| Pool | Reusable worker processes |
| ProcessPoolExecutor | Modern, clean pool interface |
| Value/Array | Shared memory primitives |
| Manager | Shared complex objects (dict, list) |
| Queue | Thread/process-safe communication |
| Pipe | Two-way process communication |
Multiprocessing vs Alternatives
| Scenario | Best Choice |
|---|---|
| CPU-heavy calculation | Multiprocessing |
| Network I/O | Threading or asyncio |
| File I/O | Threading |
| Many small tasks | Pool with chunksize |
| Large shared data | SharedMemory (Python 3.8+) |
| NumPy operations | NumPy (already parallel) |
Next Steps
In the next lesson, we'll explore Async/Await Fundamentals—understand event loops, write coroutines, use asyncio for concurrent I/O, and build async patterns for production code.
Ready for non-blocking Python? Async/await awaits!