如何在運行前啓動兩個線程並鎖定它們，並且只有在解鎖時才執行？

Question

我有這樣的例子代碼來解釋我的問題：

import threading 
import time 

class thread1(threading.Thread): 

    def __init__(self, lock): 
     threading.Thread.__init__(self) 
     self.daemon = True 
     self.start()   
     self.lock = lock 

    def run(self): 
     while True: 
      self.lock.acquire(True) 
      print ('write done by t1') 
      self.lock.release() 

class thread2(threading.Thread): 

    def __init__(self, lock): 
     threading.Thread.__init__(self) 
     self.daemon = True 
     self.start()   
     self.lock = lock 

    def run(self): 
     while True: 
      self.lock.acquire(True) 
      print ('write done by t2') 
      self.lock.release() 

if __name__ == '__main__': 
    lock = threading.Lock() 
    t1 = thread1(lock) 
    t2 = thread2(lock) 

    lock.acquire(True) 

    counter = 0 

    while True: 
     print("main...") 
     counter = counter + 1 
     if(counter==5 or counter==10): 
      lock.release() # Here I want to unlock both threads to run just one time and then wait until I release again 
     time.sleep(1) 

    t1.join() 
    t2.join() 

我遇到一些問題如下：

我想有兩個線程（線程1和線程），它們在推出開始該程序的，但它們應該等到main()counter達到5或10

當main()counter達到5或10，但應信號/觸發/解鎖的螺紋，兩者threads應只運行一次，然後等到新的unlock。

我期待的代碼具有以下輸出（每行是1秒運行）：

main... 
main... 
main... 
main... 
main... 
write done by t1 
write done by t2 
main... 
main... 
main... 
main... 
main... 
write done by t1 
write done by t2 

相反，我有不同的行爲，例如與起始：

write done by t1 
write done by t1 
write done by t1 
write done by t1 

（等）

並經過5秒

write done by t2 

很多次...

有人可以幫我解釋什麼是錯的，我該如何改善這一點？

Answer 1

1. 在線程1和線程的_ _初始化_ _（），啓動（）被分配self.lock之前被調用。
2. t1和t2是在主線程獲取鎖之前創建的。這使得這兩個線程在主線程鎖定它們之前開始打印。這是您的代碼打印前幾行「由x完成寫入」的原因。
3. 計數器達到5後，主線程釋放該鎖，但不會再次鎖定該鎖。這使得t1和t2繼續運行。
4. ，除非你殺了它，它決不會退卻...

我建議你使用Condition Object而不是鎖定。

這裏是一個基於你的代碼的例子。

import threading 
import time 


class Thread1(threading.Thread): 
    def __init__(self, condition_obj): 
     super().__init__() 
     self.daemon = True 
     self.condition_obj = condition_obj 
     self.start() 

    def run(self): 
     with self.condition_obj: 
      while True: 
       self.condition_obj.wait() 
       print('write done by t1') 


class Thread2(threading.Thread): 
    def __init__(self, condition_obj): 
     super().__init__() 
     self.daemon = True 
     self.condition_obj = condition_obj 
     self.start() 

    def run(self): 
     with self.condition_obj: 
      while True: 
       self.condition_obj.wait() 
       print('write done by t2') 


if __name__ == '__main__': 
    condition = threading.Condition() 
    t1 = Thread1(condition) 
    t2 = Thread2(condition) 

    counter = 0 

    while True: 
     print("main...") 
     counter += 1 
     if counter == 5 or counter == 10: 
      with condition: 
       condition.notify_all() 
     time.sleep(1) 

    t1.join() 
    t2.join()