Any example how to load `.wasm` in python

[am2222]

Hi, I am working on a wasm package and I am using emscripten to compile a code to .wasm I was wondering if there is an clear example how to load a .wasm using wasmtime-py?

[womeier]

Hello, did you check the examples folder?

e.g. hello.py has an example on how to use Module.from_file

[am2222]

@womeier thanks! I checked those examples and they load wat files. Does the api support .wasm too? I will try that!

Thanks!

[alexcrichton]

Yes *.wasm is supported. All the examples use *.wat to avoid checking binaries into the repo. If you're up for it a PR to improve documentation would be appreciated here!

[am2222]

@alexcrichton yeah sure I will add a PR to mention it in the documentations! Thanks!

[am2222]

@alexcrichton I have another question. So I am trying the following code

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

# Almost all operations in wasmtime require a contextual "store" argument to be
# shared amongst objects
store = Store()

# Here we can compile a `Module` which is then ready for instantiation
# afterwards
module = Module.from_file(store.engine, 'lib-wasm-py/lib.wasm')

#### 
# Our module needs one import, so we'll create that here.
def say_hello():
    print("Hello from Python!")


hello = Func(store, FuncType([], []), say_hello)

# And with all that we can instantiate our module and call the export!
instance = Instance(store, module, [hello])

and in this example an function called hello is defined and it is passed to theimports of the instance. How can I find out how to define this function? is there any way to get the list of the imports from .wasm file directly?

[alexcrichton]

Yes that should be possible through Module.imports

[am2222]

Thanks @alexcrichton , I tried to pass the module.imports to the Instance object but it seems their types are different. I think something that confuses me is that I am not sure where does imports: Sequence[AsExtern] comes from when we define an Instance.

[alexcrichton]

Ah yes Module.imports only gives you the type of the imports. It's up to you as an embedder to create those imports and pass them in.

If you're confused by this I might recommend using Linker instead as it's a bit more understandable about how modules are instantiated.

[am2222]

Thanks @alexcrichton !

I thought it is the imports are easy to define but it seems emscripten generates them for js and so I could easily use them in js but in python I have to define them. I am checking Linker docs now to get a grasp about their usage!

[yeqown]

@am2222 Any progress here? I'm confused too, when I coding a wasm in RUST, it worked in JavaScript easily with generated binding, But how to get the bindings in python. I have no idea about this.

[alexcrichton]

I believe this was answered and there are examples, so I'm going to close this.