Test calling a python coroutine (async def) from a regular function

Question

Let's say I have some asyncio coroutine which fetches some data and returns it. Like this:

async def fetch_data(*args):
  result = await some_io()
  return result

Basically this coroutine is called from the chain of coroutines, and initial coroutine is runned by creating a task. But what if for test purposes I want to run only one coroutine this way just when running some file:

if __name__ == '__main__':
  result = await fetch_data(*args)
  print(result)

And obviously I can't do this since I'm trying to run and await coroutine from not coroutine function. So the question is: is there some correct way to get data from coroutine without calling it function? I can make some Future object for result and await it, but maybe there are some other more simple and clearer ways?

Udi Udi · Accepted Answer · 2016-12-22T13:37:17

You will need to create an event loop to run your coroutine:

import asyncio

async def async_func():
    return "hello"

loop = asyncio.get_event_loop()
result = loop.run_until_complete(async_func())
loop.close()

print(result)

Or as a function:

def run_coroutine(f, *args, **kwargs):
    loop = asyncio.get_event_loop()
    result = loop.run_until_complete(f(*args, **kwargs))
    loop.close()
    return result

Use like this:

print(run_coroutine(async_func))

Or:

assert "expected" == run_coroutine(fetch_data, "param1", param2="foo")

Test calling a python coroutine (async def) from a regular function

1 Answers