threading模块之Semaphore
import threading
import time
import random
# The optional argument gives the initial value for the internal counter;
# it defaults to 1.
# If the value given is less than 0, ValueError is raised.
semaphore = threading.Semaphore(0)
def consumer():
print("consumer is waiting.")
# Acquire a semaphore
semaphore.acquire()
# The consumer have access to the shared resource
print("Consumer notify : consumed item number %s " % item)
def producer():
global item
time.sleep(10)
# create a random item
item = random.randint(0, 1000)
print("producer notify : produced item number %s" % item)
# Release a semaphore, incrementing the internal counter by one.
# When it is zero on entry and another thread is waiting for it
# to become larger than zero again, wake up that thread.
semaphore.release()
if __name__ == '__main__':
for i in range (0,5) :
t1 = threading.Thread(target=producer)
t2 = threading.Thread(target=consumer)
t1.start()
t2.start()
t1.join()
t2.join()
print("program terminated")输出：