Python Event set()用法及代码示例

Python Event.set() 方法

set() 是 Python 中线程模块的 Event 类的内置方法。

当。。。的时候set()方法被调用，该事件类对象的内部标志被设置为真。作为set()方法被一个对象调用，所有等待该事件对象的线程都被唤醒。

模块：

    from threading import Event

用法:

    set()

参数：

• None

返回值：

这个方法的返回类型是<class 'NoneType'>.该方法不返回任何内容。它将事件对象的内部标志设置为真。

范例1：

# Python program to explain the
# use of set() method in Event() class
import threading
import time

def helper_function(event_obj, timeout,i):
  # Thread has started, but it will wait 10 seconds 
  # for the event  
  print("Thread started, for the event to set")
 
  flag = event_obj.wait(timeout)
  if flag:
    print("Event was set to true() earlier, moving ahead with the thread")
  else:
    print("Time out occured, event internal flag still false. Executing thread without waiting for event")
    print("Value to be printed=", i)
    
if __name__ == '__main__':
  # Initialising an event object
  event_obj = threading.Event()
  
  # starting the thread who will wait for the event
  thread1 = threading.Thread(target=helper_function, args=(event_obj,10,27))
  thread1.start()
  # sleeping the current thread for 5 seconds
  time.sleep(5)
  
  # generating the event
  event_obj.set()
  print("Event is set to true. Now threads can be released.")
  print()

输出：

Thread started, for the event to set
Event is set to true. Now threads can be released.
Event was set to true() earlier, moving ahead with the thread

范例2：

# Python program to explain the
# use of set() method in Event() class
import threading
import time

def helper_function(event_obj, timeout,i):
  # Thread has started, but it will wait 3 seconds 
  # for the event  
  print("Thread started, for the event to set")
 
  flag = event_obj.wait(timeout)
  if flag:
    print("Event was set to true() earlier, moving ahead with the thread")
  else:
    print("Time out occured, event internal flag still false. Executing thread without waiting for event")
    print("Value to be printed=", i)
    
if __name__ == '__main__':
  # Initialising an event object
  event_obj = threading.Event()
  
  # starting the thread who will wait for the event
  thread1 = threading.Thread(target=helper_function, args=(event_obj,3,27))
  thread1.start()
  # sleeping the current thread for 5 seconds
  time.sleep(5)
  
  # generating the event
  event_obj.set()
  print("Event is set to true. Now threads can be released.")
  print()

输出：

Thread started, for the event to set
Time out occured, event internal flag still false. Executing thread without waiting for event
Value to be printed= 27
Event is set to true. Now threads can be released.