python thread-condition()简单示例
#!/usr/bin/env python
# -*-coding:utf-8-*-
import threading
import time
condition = threading.Condition()
products = 0
class Producer(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def run(self):
global condition, products
while True:
if condition.acquire():
if products < 10:
products += 1
print("Producer(%s):deliver one, now products:%s" % (self.name, products))
condition.notify()
else:
print ("Producer(%s):already 10, stop deliver, now products:%s" %(self.name, products))
condition.wait()
condition.release()
time.sleep(2)
class Consumer(threading.Thread):
def __init__(self):
threading.Thread.__init__(self)
def run(self):
global condition, products
while True:
if condition.acquire():
if products > 1:
products -= 1
print("Consumer(%s):consume one, now products:%s" % (self.name, products))
condition.notify()
else:
print("Consumer(%s):only 1, stop consume, products:%s" %(self.name, products))
condition.wait()
condition.release()
time.sleep(1)
if __name__ == "__main__":
for q in range(0, 10):
p = Producer()
p.start()
for i in range(0,2):
c = Consumer()
c.start()
执行结果：
Producer(Thread-1):deliver one, now products:1 Producer(Thread-2):deliver one, now products:2 Producer(Thread-3):deliver one, now products:3 Producer(Thread-4):deliver one, now products:4 Producer(Thread-5):deliver one, now products:5 Producer(Thread-6):deliver one, now products:6 Producer(Thread-7):deliver one, now products:7 Producer(Thread-8):deliver one, now products:8 Producer(Thread-9):deliver one, now products:9 Producer(Thread-10):deliver one, now products:10 Consumer(Thread-11):consume one, now products:9 Consumer(Thread-12):consume one, now products:8 Consumer(Thread-12):consume one, now products:7 Consumer(Thread-11):consume one, now products:6 Producer(Thread-10):deliver one, now products:7 Producer(Thread-7):deliver one, now products:8 Producer(Thread-4):deliver one, now products:9 Producer(Thread-3):deliver one, now products:10 Producer(Thread-2):already 10, stop deliver, now products:10 Producer(Thread-8):already 10, stop deliver, now products:10 Producer(Thread-6):already 10, stop deliver, now products:10 Producer(Thread-9):already 10, stop deliver, now products:10 Producer(Thread-5):already 10, stop deliver, now products:10 Producer(Thread-1):already 10, stop deliver, now products:10 Consumer(Thread-11):consume one, now products:9 Consumer(Thread-12):consume one, now products:8 Consumer(Thread-11):consume one, now products:7 Consumer(Thread-12):consume one, now products:6 Producer(Thread-4):deliver one, now products:7 Producer(Thread-3):deliver one, now products:8 Producer(Thread-10):deliver one, now products:9 Producer(Thread-7):deliver one, now products:10 Producer(Thread-2):already 10, stop deliver, now products:10 Producer(Thread-8):already 10, stop deliver, now products:10 Consumer(Thread-12):consume one, now products:9 Consumer(Thread-11):consume one, now products:8 Producer(Thread-9):deliver one, now products:9 Producer(Thread-6):deliver one, now products:10 Consumer(Thread-11):consume one, now products:9 Consumer(Thread-12):consume one, now products:8 Producer(Thread-3):deliver one, now products:9 Producer(Thread-1):deliver one, now products:10 Producer(Thread-10):already 10, stop deliver, now products:10 Producer(Thread-5):already 10, stop deliver, now products:10 Producer(Thread-7):already 10, stop deliver, now products:10 Producer(Thread-4):already 10, stop deliver, now products:10 Producer(Thread-8):already 10, stop deliver, now products:10 Producer(Thread-2):already 10, stop deliver, now products:10 Consumer(Thread-12):consume one, now products:9 Consumer(Thread-11):consume one, now products:8 Producer(Thread-6):deliver one, now products:9 Producer(Thread-9):deliver one, now products:10 Consumer(Thread-12):consume one, now products:9 Consumer(Thread-11):consume one, now products:8
......
Condition类：条件变量对象能让一个线程停下来，等待其它线程满足了某个“条件”。如，状态的改变或值的改变。
- acquire 给线程上锁
- wait wait方法释放当前线程占用的锁，同时挂起线程，直至被唤醒或超时（需timeout参数）。当线程被唤醒并重新占有锁的时候，程序才会继续执行下去。
- notify 唤醒一个挂起的线程（如果存在挂起的线程）。注：notify()方法不会释放所占用的锁。
- notifyall 调用这个方法将通知等待池中所有线程，这些线程都将进入锁定池尝试获得锁定。此方法不会释放锁定。使用前线程必须已获得锁定，否则将抛出异常。
比较经典的例子是下面这个生产者与消费者的例子，这个例子网上一搜到处都是，这里简单解释一下这段代码的意义，代码中写了两个类，Consumer和Producer，分别继承了Thread类，我们分别初始化这两个类获得了c和p对象，并启动这两个线程。则这两个线程去执行run方法（这里与Thread类内部的调度有关），定义了producer全局变量和condition对象为全局变量，当producer不大于1时，消费者线程被condition对象阻塞，不能继续消费（这里是不再递减），当producer不小于10时，生产者线程被condition对象阻塞，不再生产（这里是不再累加）.
