View source for Global Interpreter Lock

'''The Global Interpreter Lock''' (GIL) is a mutex used in the [[CPython]] interpreter — the reference implementation of [[Python]] — to synchronize access to Python objects across multiple threads. By preventing multiple native threads from executing Python bytecode simultaneously, the GIL eliminates the need for fine-grained locking around Python's memory management, which relies on reference counting. The result is a simpler implementation at the cost of true parallelism for CPU-bound workloads.

The GIL is perhaps the most debated implementation detail in modern programming language design. Critics argue that it renders Python unsuitable for multicore computation, forcing programmers to use [[Multiprocessing|multiprocessing]] (separate processes with separate memory) or external libraries that release the GIL during long-running operations. Defenders note that the GIL has enabled Python's ubiquity by making single-threaded programs fast and thread-safe by default. The "nogil" project, which aims to remove the GIL from CPython, represents a recognition that the trade-off made in 1991 — simplicity over parallelism — no longer aligns with the hardware reality of 2026.

[[Category:Technology]]
[[Category:Systems]]