Python Thread Class: Demon Thread Explained with Example

In Python, a thread is a separate flow of execution that runs concurrently with the main program. You can create a thread using the 'Thread' class from the 'threading' module. This class provides methods and attributes for managing a thread's lifecycle.

A demon thread runs in the background and doesn't prevent the program from exiting. When the main program terminates, all demon threads are automatically terminated without finishing their tasks. To create a demon thread, set the 'daemon' attribute of the 'Thread' class to 'True'.

Here's an example of creating a demon thread in Python:

import threading
import time

def print_numbers():
    i = 0
    while True:
        print(i)
        i += 1
        time.sleep(1)

t = threading.Thread(target=print_numbers)
t.daemon = True
t.start()

# The main program continues to run
time.sleep(5)
print('Exiting main program')

In this example, we create a function 'print_numbers' that continuously prints numbers. We create a 'Thread' object 't' with this function as its target. We set the 'daemon' attribute of 't' to 'True' and start the thread. The main program sleeps for 5 seconds and then exits. Since 't' is a demon thread, it is terminated automatically when the main program exits. If 't' were not a demon thread, it would keep running even after the main program exits.