CODEWITHSUNDEEP
python
Kevin Etore
Kevin Etore

Reputation: 1124

Run while loop until function has returned a value

I'm trying to light a 5mm LED while a function is running. When this function (more details about this below) is finished and has returned a value I would like to break the while loop.

Current code for while loop:

pins = [3,5,8,15,16]

def piBoard(): 
  finished = 0
  while finished!=10:
    for pin in pins
      GPIO.output(
        pin, GPIO.HIGH
      )
      time.sleep(0.1)
      GPIO.output(
        pin, GPIO.LOW
      )
    finished+=1

Now in the above example I just run the while loop until the count is equal to 10, not best practice. I would like the while loop to break if my next function has returned a value.

Function I want to break my while loop when returned its value

def myFunction():
  Thread(target = piBoard().start()
  // Trying to recognize the song
  return the song which is recognized

Thanks, - K.

Upvotes: 0

Views: 3228

Answers (5)

mlyy
mlyy

Reputation: 66

Using decorator and asyncio, inspired by @Eric Ed Lohmar:

import asyncio

def Blink():
    from functools import wraps
    async def _blink():
        while True:
            print("OFF")
            await asyncio.sleep(.5)
            print("ON")
            await asyncio.sleep(.5)

    def Blink_decorator(func):
        @wraps(func)
        async def wrapper(*args,**kwargs):
            asyncio.ensure_future(_blink())
            await func(*args,**kwargs)
        return wrapper

    return Blink_decorator

@Blink()
async def longTask():
    print("Mission Start")
    await asyncio.sleep(3)
    print("Mission End")

def main():
    loop = asyncio.get_event_loop()
    loop.run_until_complete(longTask())

Upvotes: 0

Asav Patel
Asav Patel

Reputation: 1162

if you are open to using threads. you can achieve this by using threads. here's the example code

from concurrent.futures._base import as_completed
from concurrent.futures.thread import ThreadPoolExecutor

WORK_FINISHED = False

def piBoard(): 
  while not WORK_FINISHED:
    # Do some stuff
    # Drink some coffee

def myFunction():
  time.sleep(5)
  global WORK_FINISHED
  WORK_FINISHED = True #update gobal status flag
  return something

if __name__ == '__main__':
    futures = []
    MAX_WORKERS = 5 #max number of threads you want to create
    with ThreadPoolExecutor(MAX_WORKERS) as executor:
        executor.submit(piBoard)
        # submit your function to worker thread
        futures.append(executor.submit(myFunction))

    # if you need to get return value from `myFunction`
    for fut in as_completed(futures):
        res = fut.result()

Hope this helps.

Upvotes: 0

nimish
nimish

Reputation: 4992

You need some kind of inter-thread communication. threading.Event is about as simple as you can get.

import threading

song_recognized_event = threading.event()

in your song recognizer, call set() once the song is recognized.

In your LED loop, check isSet() occasionally while toggling LEDs.

while not song_recognized_event.isSet():
    # toggle LEDs

Run clear() to reset it.

Upvotes: 0

Eric Ed Lohmar
Eric Ed Lohmar

Reputation: 1922

It sounds to me like you want to write a class that extends Thread and implements __enter__ and __exit__ methods to make it work in the with statement. Simple to implement, simple syntax, works pretty well. The class will look like this:

import threading

class Blinky(threading.Thread):
    def __init__(self):
        super().__init__()
        self.daemon = True
        self._finished = False

    def __enter__(self):
        self.start()

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.stop()

    def run(self):
        # turn light on
        while not self._finished:
            time.sleep(.5)

        # turn light off

    def stop(self):
        self._finished = True

Then, to run your function, you simply put:

with Blinky():
    my_function()

The light should turn on once the with statement is reached and turn off up to a half second after the context of the with is exited.

Upvotes: 2

Filippos Ser
Filippos Ser

Reputation: 386

In while condition put true and in while loop put if statement which will check if your function return any value if return write break

Upvotes: 0

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