Pyjion drop-in JIT compiler for CPython 3.9. Pyjion can make your Python code execute faster without any code changes.

Trying Pyjion

Checkout the live Pyjion compiler and disassembler sandbox at


Installing Pyjion

Pyjion is best installed from PyPi within a Python 3.9 virtual environment. There are binary wheels for macOS, Linux and Windows. Make sure you have updated pip before installing.

To install from PyPi, use pip to install from a virtual environment:

$ python -m pip install pyjion

Using Pyjion

After following the installation steps, pyjion is a python module that you can import a Python 3.9 environment.

After importing pyjion, enable it by calling pyjion.enable() which sets a compilation threshold to 0 (the code only needs to be run once to be compiled by the JIT):

>>> import pyjion
>>> pyjion.enable()

Any Python code you define or import after enabling pyjion will be JIT compiled. You don’t need to execute functions in any special API, its completely transparent:

>>> def half(x):
...    return x/2
>>> half(2)

Pyjion will have compiled the half function into machine code on-the-fly and stored a cached version of that compiled function inside the function object. You can see some basic stats by running, where f is the function object:

{'failed': False, 'compiled': True, 'run_count': 1}

You can also execute Pyjion against any script or module:


Or, for an existing Python module:

pyjion -m calendar

For a full list of options, see the API Reference.