You can install this extension via:

pip install wasmtime

Currently only x86_64 Windows, macOS, and Linux are supported for this Python extension.

An example of compiling a module and importing functionality from Python can be done with:

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(module, [hello])
instance.get_export("run").func().call()

Be sure to check out the examples directory which has other usage patterns as well as the full API documentation

If your wasm modules works this way, then you can also import the wasm module directly into Python without 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

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

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 send 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. This extension expects your platform's shared library to exist at wasmtime/wasmtime.pyd. You can download the latest development version of Wasmtime with python download-wasmtime.py (this is what CI does). 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 make sure it works by running all the tests:

$ pip install pytest
$ pytest

And after that you should be good to go!

It's intended that this module is a largely automated process for all of the particulars. The CI for this project does a few different things:

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

Otherwise all commits/PRs run the full test suite and also check for style with flake8