async-cast 0.3

Why async_cast?

I found the current asyncio tools frustrating when migrating from blocking code. If you want to profit IO operations to “run something else” you need to rewrite all code to use asyncio. When you start form scratch that’s acceptable, but not with legacy code.

So with this small self-contained library you can easily convert legacy code into async code. The best way is running several blocking function in different threads. But be aware that threads also bring race conditions, so make sure concurrent functions are thread-safe.

Installing

pip install -U async_cast

Casting async function to a blocking function

from async_cast import also_blocking

@also_blocking
async def request_url(url, **kwargs):
    print(f'Requestion {url} with options {kwargs}')
    ...
    result = f'<h1>{url}</h1>'
    return result

if __name__ == '__main__':
    print(request_url.sync('https://github.com'))

Casting a blocking function to async function

from async_cast import also_blocking, also_async, thread_pool

from async_cast import also_async
import asyncio

@also_async
def request_url(url, **kwargs):
    print(f'Requestion {url} with options {kwargs}')
    ...
    result = f'<h1>{url}</h1>'
    return result

async def main():
    print(await request_url.async_('https://github.com'))

if __name__ == '__main__':
    asyncio.run(main())

Running async function in threadpool

from async_cast import also_blocking, thread_pool
import asyncio

@also_blocking
async def request_url(url, **kwargs):
    print(f'Requestion {url} with options {kwargs}')
    ...
    result = f'<h1>{url}</h1>'
    return result

async def main():
    with thread_pool(3):
        t1 = request_url.async_thread('https://github.com')
        t2 = request_url.async_thread('https://google.com')
        t3 = request_url.async_thread('https://facebook.com')
        results = await asyncio.gather(t1,t2,t3)
        print(results)

if __name__ == '__main__':
    asyncio.run(main())

Running sync/blocking function in threadpool

from async_cast import also_async, thread_pool
import asyncio

@also_async
def request_url(url, **kwargs):
    print(f'Requestion {url} with options {kwargs}')
    ...
    result = f'<h1>{url}</h1>'
    return result

async def main():
    with thread_pool(3):
        t1 = request_url.async_thread('https://github.com')
        t2 = request_url.async_thread('https://google.com')
        t3 = request_url.async_thread('https://facebook.com')
        results = await asyncio.gather(t1,t2,t3)
        print(results)

if __name__ == '__main__':
    asyncio.run(main())