python避免死結方法執行個體分析

本文執行個體講述了python避免死結方法。分享給大家供大家參考。具體分析如下：

當兩個或者更多的線程在等待資源的時候就會產生死結，兩個線程相互等待。
在本文執行個體中 thread1 等待thread2釋放block , thread2等待thtead1釋放ablock，

避免死結的原則：

1. 一定要以一個固定的順序來取得鎖，這個列子中，意味著首先要取得alock, 然後再去block

2. 一定要按照與取得鎖相反的順序釋放鎖，這裡，應該先釋放block,然後是alock

import threading ,timea = 5alock = threading.Lock()b = 5block = threading.Lock()def thread1calc():  print "thread1 acquiring lock a"  alock.acquire()  time.sleep(5)  print "thread1 acquiring lock b"  block.acquire()  a+=5  b+=5  print "thread1 releasing both locks"  block.release()  alock.release()def thread2calc():  print "thread2 acquiring lock b"  block.acquire()  time.sleep(5)  print "thread2 acquiring lock a"  alock.acquire()  time.sleep(5)  a+=10  b+=10  print "thread2 releasing both locks"  block.release()  alock.release()t = threading.Thread(target = thread1calc)t.setDaemon(1)t.start()t = threading.Thread(target = thread2calc)t.setDaemon(2)t.start()while 1:  time.sleep(300)

輸出：

thread1 acquiring lock athread2 acquiring lock bthread1 acquiring lock bthread2 acquiring lock a

希望本文所述對大家的Python程式設計有所協助。

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