Async functions

Modal natively supports async/await syntax using asyncio.

First, let’s import some global stuff.

import sys

import modal

app = modal.App("example-hello-world-async")

Defining a function 

Now, let’s define a function. The wrapped function can be synchronous or asynchronous, but calling it in either context will still work. Let’s stick to a normal synchronous function

@app.function()
def f(i):
    if i % 2 == 0:
        print("hello", i)
    else:
        print("world", i, file=sys.stderr)

    return i * i

Running the app with asyncio 

Let’s make the main entrypoint asynchronous. In async contexts, we should call the function using await or iterate over the map using async for. Otherwise we would block the event loop while our call is being run.

@app.local_entrypoint()
async def run_async():
    # Call the function using .remote.aio() in order to run it asynchronously
    print(await f.remote.aio(1000))

    # Parallel map.
    total = 0
    # Call .map asynchronously using using f.map.aio(...)
    async for ret in f.map.aio(range(20)):
        total += ret

    print(total)