A Smallest Example for Multi-threading in Python with Event and Lock

Thanks to Jacob Zhong’s help. This is quite useful!

from flask import Flask
import threading
import time
import random

data = []
signal = threading.Event()
lock = threading.Lock()


class Random(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        while True:
            n = random.random()
            # print("Produces", n)
            lock.acquire()
            data.append(n)
            lock.release()
            if len(data) >= 10:
                signal.set()
            time.sleep(0.1)


class Sum(threading.Thread):
    def __init__(self):
        threading.Thread.__init__(self)

    def run(self):
        while True:
            signal.wait()
            with lock:
                # print("\nConsumes", sum(data))
                data.clear()
            time.sleep(0.1)
            signal.clear()


# create new 
produce = Random()
consume = Sum()

# start to run
produce.start()
consume.start()


def create_app():
    # create and configure the app
    app = Flask(__name__, instance_relative_config=True)

    # a simple page that says hello
    @app.route('/hello')
    def hello():
        with lock:
            return str(data[0])

    return app