Understanding Python's GIL and Multithreading Limitations

Came across a video that helped clarify something I had long used in Python, but never fully understood under the hood — multithreading and the role of the GIL. In short, when using Python’s default CPython interpreter, threads are protected by a Global Interpreter Lock (GIL). This lock ensures thread safety and prevents race conditions when multiple threads try to access shared memory. However, the trade-off is that only one thread executes Python bytecode at a time, meaning true CPU-bound parallelism isn’t achieved even if multiple threads exist. On reading more about this, it became clear why Python multithreading works well for I/O-bound tasks but struggles with CPU-bound workloads. When a thread is waiting on I/O (like network calls, file reads, or database queries), it releases the GIL, allowing another thread to run. This makes multithreading effective for I/O-heavy applications. However, for CPU-intensive operations, threads continuously compete for the GIL, so execution remains effectively single-core, limiting true parallelism despite multiple threads. Interestingly, this sheds light on why performance-critical libraries like NumPy, Pandas, etc. are largely implemented in C/C++ (and increasingly Rust). These languages operate outside the GIL, allowing actual parallel execution and helping bypass interpreter-level bottlenecks. There are also alternative Python interpreters (and Rust-based extensions) that approach concurrency differently and can utilize multi-core CPUs more effectively — depending on the use case. For a clear visual explanation, here’s the video that sparked this learning: https://lnkd.in/gx8tx82J #Python #Multithreading #GIL #CPython #Concurrency #Parallelism #SoftwareEngineering #BackendEngineering #SystemDesign #Programming

Why Python Is Removing The GIL

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Friend me I ran out of request kinda what I’m going dm about

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If you don’t mind lol

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