满足特定条件时如何防止其他线程运行？答案

【问题标题】：How can I prevent other threads from running when a certain condition is met?满足特定条件时如何防止其他线程运行？
【发布时间】：2022-08-24 22:27:17
【问题描述】：

我创造了两个线程连续运行的情况。我的目的是在输入 \"printAlphabet\" 函数的 \"Printing Alphabet\" 部分时阻止所有其他线程运行，并且当这个优先线程完成运行时，所有线程恢复执行直到再次满足条件。即使进入此部分，\"anotherThread\" 函数也会继续运行。我知道 Lock 并不是真正的方法，所以如果有人能指出我的解决方案，我将不胜感激。我在一个更大的程序中遇到了同样的情况，并且性能下降非常严重，因为我想要优先考虑的某些操作不允许完成，因为其他线程继续运行。

这是我的代码：

import threading, string, random, time

lock = threading.Lock()

def anotherThread():
  print(\"Running anotherThread\",flush=True)

def printAlphabet():
  print(\"Running printAlphabet\", flush=True)
  rand = random.randint(0,1000)
  print(rand)
  if rand < 250:
    with lock:
      print(\"Printing Alphabet\",flush=True)
      for letter in string.ascii_lowercase:
        print(letter, end =\" \", flush=True)
        time.sleep(0.1)

def main():
  while True:
    tList = [
      threading.Thread(target=anotherThread),
      threading.Thread(target=printAlphabet),
    ]
    for t in tList:
      t.start()
      time.sleep(0.5)

main()

谢谢你的帮助。

标签： python python-3.x multithreading python-multithreading

【解决方案1】：

尝试使用threading.Events 来暂停其他线程的执行：


import threading, string, random, time


def anotherThread(is_printing_alphabet: threading.Event):
    this_thread = threading.current_thread().name

    print(f"Running {this_thread}...")

    i = 0

    while i < 10:
        while not is_printing_alphabet.is_set():
            print(f'Processing {i} from {this_thread}...')
            time.sleep(1) # processing here
            i += 1

    print(f'Running {this_thread}...Done')

def printAlphabet(is_printing_alphabet: threading.Event):

    print("Printing Alphabet! All threads stops!")
    is_printing_alphabet.set() 
    for letter in string.ascii_lowercase:
        print(str(letter))
        time.sleep(0.01)
    print('All threads may resume...')
    is_printing_alphabet.clear()

def main():
    is_printing_alphabet = threading.Event()

    threads = [
        threading.Thread(target=anotherThread, daemon=True, args=(is_printing_alphabet,)),
        threading.Thread(target=anotherThread, daemon=True, args=(is_printing_alphabet,)),
    ]

    for thread in threads:
        thread.start()

    time.sleep(2)

    print_alphabet = threading.Thread(target=printAlphabet, args=(is_printing_alphabet,))
    print_alphabet.start()

    print_alphabet.join()

    time.sleep(5)

    for thread in threads:
        thread.join()

main()

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