Synchronization primitive typically used when a thread is interested in an event or state change.
Classic problem: producer-consumer problem.
# Create data queue and a condition variable
data = []
cv = threading.Condition()
# Consumer thread
def consume_item():
cv.acquire() # Acquire the lock
while not len(data):
cv.wait() # Wait for data to show up
r = data.pop()
cv.release() # Release the lock
return r
# Producer thread
def produce_item(obj):
cv.acquire() # Acquire the lock
data.append(obj)
cv.notify() # Notify a consumer
cv.release() # Release the lock