The global interpreter lock in python

The Global Interpreter Lock in Python

Python is a popular programming language known for its simplicity and readability. However, one aspect of Python that can sometimes cause confusion is the Global Interpreter Lock (GIL). In this blog post, we’ll explain what the GIL is, why it exists, and how it affects performance in Python.

What is the Global Interpreter Lock in Python?

The GIL is a mechanism in the CPython implementation of Python that prevents multiple native threads from executing Python bytecodes simultaneously. This means that even on multi-core systems, only one thread can execute Python code at a time. This can lead to performance issues, especially in multi-threaded applications.

Why does the GIL exist?

The GIL was implemented to simplify memory management in the CPython interpreter. Without the GIL, it would be much more difficult to manage memory and prevent race conditions. Additionally, the GIL makes it easier to use Python extensions written in C, which are not thread-safe.

How does the GIL affect performance in Python?

The GIL can have a significant impact on the performance of multi-threaded Python applications. Since only one thread can execute Python bytecode at a time, other threads must wait their turn to run. This can lead to a reduction in performance, especially on multi-core systems. However, it’s worth noting that many Python applications are IO-bound and not CPU-bound, so the GIL may not have a big impact on performance in these cases.

How to work around the GIL?

Using multiple processes

One way to work around the GIL is to use multiple processes instead of threads. This allows for true parallelism on multi-core systems.

Using Python extension libraries

Another way is to use Python extension libraries that release the GIL, such as NumPy and pandas, which are designed to work with large data sets.


The Global Interpreter Lock is an important aspect of the CPython implementation of Python that can affect the performance of multi-threaded applications. Understanding the GIL and how to work around it can help you write more efficient and performant Python code.

For a more in-depth overview of the global interpreter lock within python, you can read more here.

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