PythonMonkey is a Mozilla SpiderMonkey JavaScript engine embedded into the Python VM, using the Python engine to provide the JS host environment.

This product is in an early stage, approximately 75% to MVP as of May 2023. It is under active development by Distributive Corp., https://distributive.network/. External contributions and feedback are welcome and encouraged.

The goal is to make writing code in either JS or Python a developer preference, with libraries commonly used in either language available eveywhere, with no significant data exchange or transformation penalties. For example, it should be possible to use NumPy methods from a JS library, or to refactor a slow "hot loop" written in Python to execute in JS instead, taking advantage of SpiderMonkey's JIT for near-native speed, rather than writing a C-language module for Python. At Distributive, we intend to use this package to execute our complex dcp-client library, which is written in JS and enables distributed computing on the web stack.

• Strings share immutable backing stores whenever possible (when allocating engine choses UCS-2 or Latin-1 internal string representation) to keep memory consumption under control, and to make it possible to move very large strings between JS and Python library code without memory-copy overhead.
• TypedArrays to share mutable backing stores; if this is not possible we will implement a copy-on-write (CoW) solution.
• JS objects are represented by Python dicts
• JS Date objects are represented by Python datetime.datetime objects
• Intrinsics (boolean, number, null, undefined) are passed by value
• JS Functions are automatically wrapped so that they behave like Python functions, and vice-versa

• [done] JS instrinsics coerce to Python intrinsics
• [done] JS strings coerce to Python strings
• JS objects coerce to Python dicts [own-properties only]
• [done] JS functions coerce to Python function wrappers
• [done] JS exceptions propagate to Python
• [done] Implement eval() function in Python which accepts JS code and returns JS->Python coerced values
• [done] NodeJS+NPM-compatible CommonJS module system
• [done] Python strings coerce to JS strings
• [done] Python intrinsics coerce to JS intrinsics
• Python dicts coerce to JS objects
• [done] Python require function, returns a coerced dict of module exports
• [done] Python functions coerce to JS function wrappers
• [done] CommonJS module system .py loader, loads Python modules for use by JS
• JS object->Python dict coercion supports inherited-property lookup (via getattribute?)
• Python host environment supplies event loop, including EventEmitter, setTimeout, etc.
• Python host environment supplies XMLHttpRequest (other project?)
• Python host environment supplies basic subsets of NodeJS's fs, path, process, etc, modules; as-needed by dcp-client (other project?)
• Python TypedArrays coerce to JS TypeArrays
• JS TypedArrays coerce to Python TypeArrays

1. You will need the following installed (which can be done automatically by running ./setup.sh):

   • cmake
   • doxygen
   • graphviz
   • llvm
   • rust
   • python3.8 or later with header files (python3-dev)
   • spidermonkey 102.2.0 or later
   • npm (nodejs)
   • Poetry

2. Run poetry install. This command automatically compiles the project and installs the project as well as all Python dependencies to the poetry virtualenv.

1. Compile the project
2. From the root directory, run poetry run pytest ./tests/python

See also: examples/

After compiling the project in the build/src folder you will find a .so file named pythonmonkey.so. This is the shared object file that contains the pythonmonkey module.

PythonMonkey is not release-ready yet. Our first public release is scheduled for mid-June 2023.

$ pip install pythonmonkey

$ pip install -i https://nightly.pythonmonkey.io/ --pre pythonmonkey

pythonmonkey is available in the poetry virtualenv once you compiled the project using poetry.

$ poetry run python

Python 3.10.6 (main, Nov 14 2022, 16:10:14) [GCC 11.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import pythonmonkey as pm
>>> hello = pm.eval("() => {return 'Hello from Spidermonkey!'}")
>>> hello()
'Hello from Spidermonkey!'

Alternatively, you can build a wheel package by running poetry build --format=wheel, and install it by pip install dist/*.whl.

If you are having trouble with the CommonJS require function, set DEBUG='ctx-module*' and you can see the filenames it tries to laod

Loading the CommonJS subsystem declares some extra symbols which may be helpful in debugging -

• python.print - the Python print function
• python.getenv - the Python getenv function