python 示例_Python条件类| release（）方法与示例

python 示例

Python Condition.release()方法 (Python Condition.release() Method)

release() is an inbuilt method of the Condition class of the threading module in Python.

release()是Python中线程模块的Condition类的内置方法。

Condition class implements condition variable objects. A condition variable allows one or more threads to wait until they are notified by another thread. release() method is used to release the lock which has been acquired by the calling thread in order to free the critical section of the code. Once the lock is released, it can be acquired by some other threads waiting for its turn to use the lock.

条件类实现条件变量对象 。条件变量允许一个或多个线程等待，直到被另一个线程通知为止。 release()方法用于释放由调用线程获取的锁，以释放代码的关键部分。释放锁后，其他一些线程可以获取该锁，等待其轮换使用该锁。

Read about Producer-Consumer here: Condition.acquire() Method

在这里阅读有关Producer-Consumer的信息： Condition.acquire()方法

Module:

模块：

    from threading import Condition

Syntax:

句法：

    release()

Parameter(s):

参数：

None
没有

Return value:

返回值：

The return type of this method is <class 'NoneType'>. The method is used to release the underlying lock which is acquired by a given thread.

此方法的返回类型为<class'NoneType'> 。该方法用于释放由给定线程获取的基础锁。

Example:

例：

# Python program to explain the
# use of release() method for Condition object
import threading
import time
import random
class subclass:
# Initialising the shared resources
def __init__(self):
self.x = []
# Add an item for the producer
def produce_item(self, x_item):
print("Producer adding an item to the list")
self.x.append(x_item)
# Consume an item for the consumer
def consume_item(self):
print("Consuming from the list")
consumed_item = self.x[0]
print("Consumed item: ", consumed_item)
self.x.remove(consumed_item)
def producer(subclass_obj, condition_obj):
# Selecting a random number from the 1 to 3
r = random.randint(1,3)
print("Random number selected was:", r)
# Creting r number of items by the producer
for i in range(1, r):
print("Producing an item, time it will take(seconds): " + str(i))
time.sleep(i)
print("Producer acquiring the lock")
condition_obj.acquire()
try:
# Produce an item
subclass_obj.produce_item(i)
# Notify that an item  has been produced
condition_obj.notify()
finally:
# Releasing the lock after producing
condition_obj.release()
def consumer(subclass_obj, condition_obj):
condition_obj.acquire()
while True:
try:
# Consume the item 
subclass_obj.consume_item()
except:
print("No item to consume, list empty")
print("Waiting for 10 seconds")
# wait with a maximum timeout of 10 sec
value = condition_obj.wait(10)
if value:
print("Item produced notified")
continue
else:
print("Waiting timeout")
break
# Releasig the lock after consuming
condition_obj.release()
if __name__=='__main__':
# Initialising a condition class object
condition_obj = threading.Condition()
# subclass object
subclass_obj = subclass()
# Producer thread
pro = threading.Thread(target=producer, args=(subclass_obj,condition_obj,))
pro.start()
# consumer thread
con = threading.Thread(target=consumer, args=(subclass_obj,condition_obj,))
con.start()
pro.join()
con.join()
print("Producer Consumer code executed")

Output:

输出：

Random number selected was: 3
Producing an item, time it will take(seconds): 1
Consuming from the list
No item to consume, list empty
Waiting for 10 seconds
Producer acquiring the lock
Producer adding an item to the list
Item produced notified
Consuming from the list
Consumed item:  1
Consuming from the list
No item to consume, list empty
Waiting for 10 seconds
Producing an item, time it will take(seconds): 2
Producer acquiring the lock
Producer adding an item to the list
Item produced notified
Consuming from the list
Consumed item:  2
Consuming from the list
No item to consume, list empty
Waiting for 10 seconds
Waiting timeout
Producer Consumer code executed