What is threading.active_count() in Python?

Overview

In Python, the method threading.active_co unt() from the threading module is used to count the currently active or running threads.

Syntax

threading.active_count()

Parameters

N/A: This method does not take any argument value.

Return value

Count: This method returns the total currently active thread count.

Code

The code below demonstrates how to use active_count() in a program:

# Program to count active threads
# active_count() method from Threading Module
import threading
import time
# Methods for three threads..
def thread1_Subroutine(i):
    time.sleep(2)
    print("Thread-1: Number of active threads:", threading.active_count())
    print('Thread 1 Value:', i)
def thread2_Subroutine(i):
    print("Thread-2: Number of active threads:", threading.active_count())
    print('Thread 2 Value:', i)
    
def thread3_Subroutine(i):
    time.sleep(5)
    print("Thread-3: Number of active threads:", threading.active_count())
    print("Thread 3 Value:", i)
    
# Creating sample threads
thread1 = threading.Thread(target=thread1_Subroutine, args=(100,), name="Thread1")
thread2 = threading.Thread(target=thread2_Subroutine, args=(200,), name="Thread2")
thread3 = threading.Thread(target=thread3_Subroutine, args=(300,), name="Thread3")
print("START: Current active thread count: ", threading.active_count())
# Calling start() method to initialize execution
thread1.start()
thread2.start()
thread3.start()
thread3.join() # Wait for thread-3 to join.

Explanation

In the above code snippet:

  • Line 8: We use the thread1_Subroutine(i) to get the count of currently active threads.
  • Line 12: We use the thread2_Subroutine(i) to get a current active count.
  • Line 17: We use the thread3_Subroutine(i) to get the current active count.
  • Lines 21, 22, and 23: We create three threads, thread1, thread2, and thread3 with their default values like target, args, and their names.
  • Line 24: It shows the current thread count at the beginning of the program.
  • Lines 26, 27, and 28: We start all three threads created in lines 21, 22, and 23.

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