Python線程Event例子

需求1：Boss需要一個員工生產100個杯子，Boss一直等待員工生產完成之后方可

import threading
import logging
import time

logging.basicConfig(level=logging.INFO)

def worker(event:threading.Event, count=10):
    logging.info("I'm working for U.")
    cups = []
    while True:
        logging.info('make 1')
        time.sleep(0.5)
        cups.append(1)
        if len(cups) >= count:
            event.set()
            break
    logging.info('I finished my job. cups={}'.format(cups))

def boss(event:threading.Event):
    logging.info("I'm boss, waiting for U.")
    event.wait()
    logging.info("Good Job")

Event = threading.Event()
w = threading.Thread(target=worker, args=(Event, 100))
b = threading.Thread(target=boss, args=(Event, ))
w.start()
b.start()

需求2：使用threading Event實現類似Timer延遲執行的線程

思路：需要有 start和 cancel的功能(使用 Event  wait()，set()， 方法)

代碼實現：
import threading
import datetime
import logging

logging.basicConfig(level=logging.INFO)

def add(x:int, y:int):
    logging.info(x + y)

class Timer(object):
    def __init__(self, interval, fn, *args, **kwargs):
        self.interval = interval
        self.fn = fn
        self.args = args
        self.kwargs = kwargs
        self.event = threading.Event()

    def start(self):
        threading.Thread(target=self.__run).start()

    def cancel(self):
        self.event.set()

    def __run(self):
        start = datetime.datetime.now()
        logging.info('Waiting')

        self.event.wait(self.interval)
        if not self.event.is_set():
        # 上面兩行可以直接改寫成 if not self.event.wait(self.interval):
            self.fn(*self.args, **self.kwargs)
        delta = (datetime.datetime.now() - start).total_seconds()
        logging.info('finished {}'.format(delta))
        self.event.set()

t = Timer(10, add, 4, 50)
t.start()
e = threading.Event()
e.wait(4)
t.cancel()

print("主線程完成")