wasmtime 0.18.1

A WebAssembly runtime powered by Wasmtime

wasmtime-py

Python embedding of Wasmtime

A Bytecode Alliance project

Installation

To install wasmtime-py, run this command in your terminal:

$ pip install wasmtime

The package currently supports 64-bit builds of Python 3.6+ on x86_64 Windows, macOS, and Linux

Usage

In this example, we compile and instantiate a WebAssembly module and use it from Python:

from wasmtime import Store, Module, Instance, Func, FuncType

store = Store()
module = Module(store, """
  (module
    (func $hello (import "" "hello"))
    (func (export "run") (call $hello))
  )
""")

def say_hello():
    print("Hello from Python!")
hello = Func(store, FuncType([], []), say_hello)

instance = Instance(store, module, [hello])
run = instance.exports["run"]
run()

Be sure to check out the examples directory, which has other usage patterns as well as the full API documentation of the wasmtime-py package.

If your WebAssembly module works this way, then you can also import the WebAssembly module directly into Python without explicitly compiling and instantiating it yourself:

# Import the custom loader for `*.wasm` files
import wasmtime.loader

# Assuming `your_wasm_file.wasm` is in the python load path...
import your_wasm_file

# Now you're compiled and instantiated and ready to go!
print(your_wasm_file.run())

Contributing

So far this extension has been written by folks who are primarily Rust programmers, so it's highly likely that there's some faux pas in terms of Python idioms. Feel free to create a PR to help make things more idiomatic if you see something!

To work on this extension locally you'll first want to clone the project:

$ git clone https://github.com/bytecodealliance/wasmtime-py
$ cd wasmtime-py

Next up you'll acquire a Wasmtime installation. The wasmtime-py package expects your platform's shared library to exist at wasmtime/wasmtime.pyd. You can download the latest development version of Wasmtime by running a script in the top-level directory of the package's source (this is what CI does):

$ python download-wasmtime.py

Otherwise if you have a local checkout of Wasmtime you can symlink its libwasmtime.so (or equivalent) to wasmtime/wasmtime.pyd.

After you've got Wasmtime set up you can check it works by running all the unit tests:

$ pip install pytest
$ pytest

After that you should be good to go!

CI and Releases

The CI for this project does a few different things:

• API docs are generated for pushes to the main branch and are published online.
• Test coverage information is generated for pushes to the main branch and are available online.
• Each push to main will publish a release to test.pypi.org for local inspection.
• Tagged commits will automatically be published to pypi.org.

All commits/PRs run the full test suite, and check for code style and other errors using flake8.