The Quest for Parallelism: How Paul Overcame the Global Interpretor Lock in Python

Achref el karoui
2 min readOct 22, 2023

This is the continuation of Paul's adventures series, in which we will discuss Paul's quest to find parallelism in python.

In the bustling world of programming, there once was a talented young developer named Paul, he was passionate about coding and always eager to learn new concepts. One day, while working on a complex Python project, Paul came across a peculiar challenge: a global interpretor lock.

The global interpretor lock, or GIL, was a mechanism used in the CPython implementation of Python. It had the power to limit the execution of Python threads to a single thread at a time. This meant that even if multiple threads were created, they would not run concurrently due to the GIL.

Curiosity sparked within Paul, and the determined developer decided to delve deeper into this mysterious lock. After hours of research and studying, Paul discovered that the GIL was designed mainly for memory management purposes. It ensured that multiple threads did not interfere with each other's memory allocations, preventing memory corruption and maintaining the stability of the Python interpreter.

However, Paul also learned that the GIL could become a bottleneck for performance in certain scenarios. It limited the true potential of utilizing multiple cores and hindered the ability to achieve true parallelism. This sparked a desire within Paul to find a solution to harness the full power of Python's multi-threading capabilities.

Armed with newfound determination, Paul embarked on a quest to tackle the global interpretor lock. After extensive research and brainstorming, Paul devised a plan. The solution involved utilizing multiprocessing instead of multithreading, as multiprocessing bypassed the GIL's limitations by creating separate Python interpreters for each process.

Implementing this solution wasn't without its challenges. Paul had to carefully restructure the code, using shared memory or inter-process communication techniques to allow data exchange between the different processes. It required meticulous attention to detail and a deep understanding of Python's multiprocessing module.

With perseverance and a touch of genius, Paul successfully transformed the once-threaded code into a multi-process masterpiece. The formerly constrained Python project now ran efficiently and took full advantage of the available hardware resources.

So to summarize The GIL is a feature of Python that prevents multiple threads from executing Python code at the same time. It ensures that only one thread can access the Python interpreter and modify Python objects. The GIL is necessary because Python uses reference counting for memory management, which is not thread-safe. The GIL can improve the performance of single-threaded programs, but it can also limit the concurrency and scalability of multi-threaded programs

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