Python Event set()用法及代碼示例

Python Event.set() 方法

set() 是 Python 中線程模塊的 Event 類的內置方法。

當。。。的時候set()方法被調用，該事件類對象的內部標誌被設置為真。作為set()方法被一個對象調用，所有等待該事件對象的線程都被喚醒。

模塊：

    from threading import Event

用法:

    set()

參數：

• None

返回值：

這個方法的返回類型是<class 'NoneType'>.該方法不返回任何內容。它將事件對象的內部標誌設置為真。

範例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()

輸出：

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

範例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()

輸出：

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.