Python 線程（二）：簡單鎖實現線程同步

Python中有兩種鎖，一個鎖是原始的鎖（原語）， 不可重入，而另一種鎖則是可重入的鎖即遞歸鎖。而是thread模塊中，只提供了不可重入的鎖，而在threading中則提供這兩種鎖。

可重入：當一個線程擁有一個鎖的使用權后，再次獲取鎖的使用權時，不會阻塞，會立馬得到使用權，則原始鎖的話，則不行，會阻塞。

方法一：thead的不可重入鎖

　　

import thread
import time

lock = thread.allocate_lock()

def Count(id):
    global num;

    while True:
        lock.acquire()
        if num <= 10:
            print "Thread id is : %s     The num is %s\n" % (id, str(num))
            num = num + 1
        else:
            break
        lock.release()
    else:
        thread.exit_thread()

if __name__ == "__main__":
    num = 1
    thread.start_new_thread(Count, ('A',))
    thread.start_new_thread(Count, ('B',))

    time.sleep(5)

　　

方法二：theading的Lock(不可重入鎖)

import threading
import time

lock = threading.Lock()

def Count(id):
    global num;

    while True:
        lock.acquire()
        if num <= 10:

            print "Thread id is : %s     The num is %s\n" % (id, str(num))
            num = num + 1
        else:
            break
        lock.release()

if __name__ == "__main__":
    num = 1
    t1 = threading.Thread(target=Count, args=('A', ))
    t2 = threading.Thread(target=Count, args=('B', ))

    t1.start()
    t2.start()

    time.sleep(5)

　　方法三：threading的RLock(可重入)

import threading
import time

lock = threading.RLock()

def CountNum(id):
    global num
    
    lock.acquire()
    
    if num <= 10:
        print "Thread id is : %s     The num is %s\n" % (id, str(num))
        num = num + 1
        CountNum(id)

    lock.release()

if __name__ == "__main__":
    num = 1
    t1 = threading.Thread(target=CountNum, args=('A'))

    t1.start()

    time.sleep(5)