> ## Documentation Index > Fetch the complete documentation index at: https://site.aspect.build/llms.txt > Use this file to discover all available pages before exploring further. # Wasm `function` **Wasm.instantiate**

              
          def Wasm.instantiate(
          path: str,
          /,
          \*,
          args: list\[str] = \[],
          env: dict\[str, str] = ...,
          preopened\_dirs: dict\[str, str] = ...,
          inherit\_stdio: bool = True,
          imports: dict\[str, dict\[str, typing.Any]] = ...
          ) -> Instance
        
      
    

Instantiate a WASM module with optional WASI configuration and host function imports. # Example ```starlark theme={null} # In host_funcs.axl: def get_term_size(ctx, memory) -> tuple[int, int]: return (80, 24) # In main.axl: load("./host_funcs.axl", "get_term_size") instance = ctx.wasm.instantiate( "app.wasm", args = ["--verbose"], env = {"HOME": "/home/user"}, preopened_dirs = {"/tmp": "/sandbox"}, imports = { "env": { "get_term_size": get_term_size, } }, ) instance.start() # Call _start for WASI modules result = instance.exports.my_function(42) ``` # Host Function Signature Host functions receive two injected arguments followed by WASM arguments: * `ctx` - Task context (currently `None`, reserved for future use) * `memory` - WASM memory access (currently `None`, reserved for future use) * Additional arguments correspond to the WASM function signature Return values are converted back to WASM types. Use tuples for multi-value returns. **Parameters** * `path`: - Path to the WASM binary file * `args`: - Command-line arguments to pass to the WASM module (WASI) * `env`: - Environment variables to set for the WASM module (WASI) * `preopened_dirs`: - Directories to pre-open for filesystem access (WASI). Keys are host paths, values are guest paths. * `inherit_stdio`: - Whether to inherit stdin/stdout/stderr from the host (default: true) * `imports`: - Host function imports, organized by module name and function name. **Important:** Host functions must be imported from a loaded module via `load()`, not defined in the same file. This ensures they are frozen and can be safely stored in the WASM runtime.