[FIXED] How to get the returned value from asyncio loop?

Issue

I'm trying to measure the power level of the signal captured by rtl sdr dongle and then compare several measurements to get the best level of power, but I don't know exactly how to return instantly the power level to my main function.

Here is my code:

import asyncio
from rtlsdr import RtlSdr
import numpy as np
import time

global power

async def streaming():
    #SDR CONFIGURATION
    sdr = RtlSdr()
    sdr.rs = 2.4e6
    sdr.fc = 801e6

    async for samples in sdr.stream(512):
        global power
        samples = samples - np.mean(samples)
        calibrate = 3.2
        power = np.mean(np.abs(samples ** 2))

        #print('Relative power:', calibrate * 10 * np.log10(power), 'dB')
    await sdr.stop()
    sdr.close()
    #return power
# i traied this function to return the result from streaming() but it didn't work !!
async def get_result():
    global power
    while True:
        yield power

async def main():
    global power
    nb_config = 100
    fpower = -100
    for i in range(nb_config):
        # Get the current event loop.
        loop = asyncio.get_running_loop()
        #try to get the power value from the loop
        task = streaming()
        power = loop.run_until_complete(asyncio.gather(*task))
        loop.close()
        if power > fpower :
            fpower = power
            print(10*np.log10(fpower))

asyncio.run(main(), debug=True)

Solution

The short answer is that if you want an async function to yield up multiple values, just yield them:

async def powers(): # was 'streaming', but that doesn't seem to describe it
    ...

    async for samples in sdr.stream(512):
        samples = samples - np.mean(samples)
        calibrate = 3.2
        power = np.mean(np.abs(samples ** 2))
        yield power

    await sdr.stop()
    sdr.close()

But then you need to get these values inside main:

async def main():
    ...
    async for power in powers():
        print(power)

Since this is cooperative multithreading, any time python is in main() (or anything else), it won't be in powers(). Whether that matters depends on how the tools in question are built, but you might need to be careful not to full up buffers once your code gets longer, if your SDR is still putting out data.

Answered By - 2e0byo