coroutine not recognized

[haldark]

Note: I have posted this question in https://github.com/peterhinch/micropython-async also. But not sure if it is actively monitored by Peter. And since uasyncio is a platform agnostic library, I thought this forum may be suitable.

I am new to async programming in micropython. However, to get a basic hang of it I did some experiments with creating and stopping tasks at different time intervals within main(), which is surrendered in an event loop by asyncio.run(main). After few trial and errors it worked. So, I though I got the idea.

Basically, what I thought is that once the main is surrendered to the event loop, I can create objects inside the main as usual, and class methods can create_task with a coro. Those tasks will get scheduled in the event loop.

I even created a async Timer class, which also works.

Emboldened by my newly acquired success, I tried creating an Updater class, that will periodically poll a http server for updates. I am using async http class and asyc timer class.

When I use the 'http.get' method as the coro in create_task, it works.

from mylib.w5x00_lib import w5x00
import uasyncio as asyncio
import mylib.async_http as http
from mylib.async_timer import Timer as aTimer

class Updater:
    def __init__(self):
        print("Init")
        
    def begin(self, http_client, url=""):
        print("Begin")
        self._http_get = http_client.get #loading module class methods in class local variables
        self._url=url
        self._get_req_dict = {}
        self._get_resp_dict = {}
        self._timer=aTimer(name="Updater Timer", interval=5, type=2, callback=self._check_update)
        self._timer.start()
        self._count=0
        await asyncio.sleep(0)

    async def _get_manifest(self):
        self._get_resp_dict = {}
        await asyncio.sleep(0)
        self._get_resp_dict = await self._http_get(self._get_req_dict)
        

    async def _check_update(self, t_name, ud, t):
        print("Checking for updates")
        if (self._url != ""):
            self._get_req_dict["url"] = self._url + str(self._count)
            self._count += 1
            print("Creating task")
            #task = asyncio.create_task(self._get_manifest)
            task = asyncio.create_task(self._http_get(self._get_req_dict))
            print("task created")
            await asyncio.sleep(0)
            await task
            print("Manifest: {}".format(self._get_resp_dict))

def main():
    updater=Updater()
    await updater.begin(http, 'http://192.168.1.23/hello?a=')
    print("Here 1")
    while True:
        await asyncio.sleep(0)
    print("Here 2")

wiz5k = w5x00()
n = wiz5k.nic
wiz5k.begin(dhcp=True, verbose=False)
print("Ethernet I/F Connected? ", wiz5k.isconnected())
print("I/F = ", n.ifconfig())
asyncio.run(main())

Output:

..Ethernet I/F Connected?  True
I/F =  ('192.168.1.170', '255.255.255.0', '192.168.1.1', '8.8.8.8')
Init
Begin
Timer 'Updater Timer'::Initialized
Timer 'Updater Timer'::Starting with type=2
Here 1
Checking for updates
Creating task
task created
open_conn url_params: {'host': '192.168.1.23', 'path': 'hello?a=0', 'proto': 'http'}
Manifest: {}
Checking for updates
Creating task
task created
open_conn url_params: {'host': '192.168.1.23', 'path': 'hello?a=1', 'proto': 'http'}
Manifest: {}
Checking for updates
Creating task
task created
open_conn url_params: {'host': '192.168.1.23', 'path': 'hello?a=2', 'proto': 'http'}
Manifest: {}
Checking for updates
Creating task
task created
open_conn url_params: {'host': '192.168.1.23', 'path': 'hello?a=3', 'proto': 'http'}
Manifest: {}
Checking for updates
Creating task
task created
open_conn url_params: {'host': '192.168.1.23', 'path': 'hello?a=4', 'proto': 'http'}
Manifest: {}

So, Periodic async http call is working with Async Timer. However, because I have used http_get coro as argument of create_task, I am not able to capture the return response from http_get call, So, I wrapped http_get inside a coro named _get_manifest. And instead of using http_get as coro, I tried using _get_manifest coro with the create_task.

 async def _get_manifest(self):
        self._get_resp_dict = {}
        await asyncio.sleep(0)
        self._get_resp_dict = await self._http_get(self._get_req_dict)

   async def _check_update(self, t_name, ud, t):
        print("Checking for updates")
        if (self._url != ""):
            self._get_req_dict["url"] = self._url + str(self._count)
            self._count += 1
            print("Creating task")

            # ===== HERE IS THE CHANGE ===========
            task = asyncio.create_task(self._get_manifest) 
            #task = asyncio.create_task(self._http_get(self._get_req_dict))
            # ===== END OF CHANGE ===========

            print("task created")
            await asyncio.sleep(0)
            await task
            print("Manifest: {}".format(self._get_resp_dict))

But I got unexpected result.

Output:

MPY: soft reboot
..Ethernet I/F Connected?  True
I/F =  ('192.168.1.170', '255.255.255.0', '192.168.1.1', '8.8.8.8')
Init
Begin
Timer 'Updater Timer'::Initialized
Timer 'Updater Timer'::Starting with type=2
Here 1
Checking for updates
Creating task
coroutine expected

According to https://github.com/peterhinch/micropython-async/blob/master/v3/docs/TUTORIAL.md#22-coroutines-and-tasks,

The fundmental building block of uasyncio is a coro. This is defined with async def and usually contains at least one await statement.

async def bar():
    await asyncio.sleep(1)
    print('Done')

The _get_manifest follows the above template. It is defined with async def, and has await statement

  async def _get_manifest(self):
        self._get_resp_dict = {}
        self._get_resp_dict = await self._http_get(self._get_req_dict)

So, Why _get_manifest is not identified as a coro, when used in create_task?

[peterhinch]

You need

task = asyncio.create_task(self._get_manifest()) 

[haldark]

Ohh hhhh...I did not realize that just the function pointer is not enough...

Thanks a lot Peter...It will be forever etched in my mind :)