Python Lock release()用法及代碼示例

Python Lock.release() 方法

release() 是 Python 中線程模塊的 Lock 類的內置方法。

此方法釋放線程先前獲取的鎖。一旦鎖被釋放，它就可以被另一個線程獲取。這可以從任何線程調用，而不僅僅是從獲取它的線程調用。釋放未鎖定的鎖時，會引發 RuntimeError。

模塊：

    from threading import Lock

用法:

    release()

參數：

• None

返回值：

這個方法的返回類型是<class 'NoneType'>.它釋放獲得它的線程。

例：

# Python program to show
# the use of release() method in Lock class

import threading
import random
                    
class shared(object):
  
    def __init__(self, x = 0):
        # Created a Lock object
        self.lock = threading.Lock()
        self.incr = x
        
        # Increment function for the thread
    def incrementcounter(self):
        print("Waiting for the lock to be unlocked")
        # Lock acquired by the current thread
        self.lock.acquire()
        try:
            print('Lock acquired, current counter value:', self.incr)
            self.incr = self.incr + 1
        finally:
            print('Lock released, current counter value:', self.incr)
            # Lock released by the given thread
            self.lock.release()

def helper_thread(c):
    # Getting a random integer between 1 to 3
    r = random.randint(1,3)
    print("Random value selected:", r)
    for i in range(r):
      c.incrementcounter()
    print('Finished', str(threading.current_thread().getName()))
    print()

if __name__ == '__main__':
    obj = shared()

    thread1 = threading.Thread(target=helper_thread, args=(obj,))
    thread1.start()
    
    thread2 = threading.Thread(target=helper_thread, args=(obj,))
    thread2.start()

    thread1.join()
    thread2.join()
    
    print('Final counter value:', obj.incr)

輸出

Random value selected:2
Waiting for the lock to be unlocked
Lock acquired, current counter value: 0
Lock released, current counter value: 1
Waiting for the lock to be unlocked
Lock acquired, current counter value: 1
Lock released, current counter value: 2
Finished Thread-1

Random value selected:3
Waiting for the lock to be unlocked
Lock acquired, current counter value: 2
Lock released, current counter value: 3
Waiting for the lock to be unlocked
Lock acquired, current counter value: 3
Lock released, current counter value: 4
Waiting for the lock to be unlocked
Lock acquired, current counter value: 4
Lock released, current counter value: 5
Finished Thread-2

Final counter value:5