Python asyncio：函数或协程，使用哪个？

Question

I'm wondering if there are any noticeable differences in performance between foo and bar :

class Interface:
    def __init__(self, loop):
        self.loop = loop

    def foo(self, a, b):
        return self.loop.run_until_complete(self.bar(a, b))

    async def bar(self, a, b):
        v1 = await do_async_thing1(a)
        for i in range(whatever):
            do_some_syncronous_work(i)
        v2 = await do_async_thing2(b, v1)
        return v2

async def call_foo_bar(loop):
    a = 'squid'
    b = 'ink'
    interface = Interface(loop)
    v_foo = interface.foo(a, b)
    v_bar = await interface.bar(a, b)

But will the use of run_until_complete cause any practical, noticeable different to running my program?

(The reason I ask is I'm building an interface class which will accommodate decomposable "back-ends" some of which could be asynchronous. I'm hoping to use standard functions for the public (reusable) methods of the interface class so one API can be maintained for all code without messing up the use of asynchronous back-ends where an event-loop is available.)

Update: I didn't check the code properly and the first version was completely invalid, hence rewrite.

Answer 1

loop.run_until_complete() should be used outside of coroutine on very top level. Calling run_until_complete() with active (running) event loop is forbidden.

Also loop.run_until_complete(f) is a blocking call: execution thread is blocked until f coroutine or future becomes done.

async def is a proper way to write asynchronous code by making concurrent coroutines which may communicate with each other.

async def requires running event loop (either loop.run_until_complete() or loop.run_forever() should be called).

Answer 2

There is a world of difference. It is a SyntaxError to use await in a normal function def function.

import asyncio

async def atest():
    print("hello")

def test():
    await atest()

async def main():
    await atest()
    test()

--

File "test.py", line 9
    await atest()
              ^
SyntaxError: invalid syntax

Answer 3

I do not believe so. I have used both and have not really seen a difference. I prefer foo just because I have used it more and understand it a bit better, but it is up to you.