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Python Event set() Method with Example

Python Event.set() Method: In this tutorial, we will learn about the set() method of Event Class in Python with its usage, syntax, and examples. By Hritika Rajput Last updated : April 25, 2023

Python Event.set() Method

The Event.set() is an inbuilt method of the Event class of the threading module. When the set() method is called, the internal flag of that event class object is set to true. As the set() method gets called for an object, all the threads waiting for that event object get awakened.

Module

The following module is required to use set() method:

import threading

Class

The following class is required to use set() method:

from threading import Event

Syntax

The following is the syntax of set() method:

set()

Parameter(s)

The following are the parameter(s):

• None

Return Value

The return type of this method is <class 'NoneType'>. The method does not return anything. It sets the internal flag of an event object to true.

Example 1: Use of Event.set() Method

# 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()

Output

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

Example 2: Use of Event.set() Method

# 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()

Output

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.