# cond.py
#
# An example of using a condition variable to set up a producer/consumer
# problem.

import threading
import time

# A list of items that are being produced.  Note: it is actually
# more efficient to use a collections.deque() object for this.

items = []

# A condition variable for items
items_cv = threading.Condition()

# A producer thread
def producer():
    print "I'm the producer"
    for i in range(30):
        with items_cv:          # Always must acquire the lock first
            items.append(i)     # Add an item to the list
            items_cv.notify()   # Send a notification signal
        time.sleep(1)
        
# A consumer thread
def consumer():
    print "I'm a consumer", threading.currentThread().name
    while True:
        with items_cv:           # Must always acquire the lock
            while not items:     # Check if there are any items
                items_cv.wait()  # If not, we have to sleep
            x = items.pop(0)     # Pop an item off
        
        print threading.currentThread().name,"got", x
        time.sleep(5)
    

# Launch a bunch of consumers
cons = [threading.Thread(target=consumer)
        for i in range(10)]

for c in cons:
    c.setDaemon(True)
    c.start()

# Run the producer
producer()