Python sys.setswitchinterval() method

The Python sys.setswitchinterval() method which is the time in seconds that the Python interpreter will wait before switching between threads. This affects the execution of multi-threaded Python programs by allowing us to control how often the interpreter should switch context between threads.

A shorter interval can make the program more responsive but may increase overhead while a longer interval can reduce context-switching overhead but may make the program less responsive. Adjusting this interval can be useful for optimizing performance in multi-threaded applications.

Syntax

Following is the syntax and parameters of Python sys.setswitchinterval() method −

sys.setswitchinterval(interval)

Parameter

This method accepts a value representing the new thread switch interval in seconds. It should be a floating-point number representing the number of seconds.

Return value

This method does not return any value.

Example 1

Following is the basic example which sets a very short switch interval of 1 millisecond. The python sys.getswitchinterval() method is used to verify the current switch interval −

import sys

# Set a short thread switch interval
sys.setswitchinterval(0.001)
print(f"Thread switch interval set to: {sys.getswitchinterval()} seconds")

Output

Thread switch interval set to: 0.001 seconds

Example 2

Setting a long switch interval with sys.setswitchinterval() method can make the Python interpreter switch between threads less frequently. This example sets a longer switch interval of 0.1 seconds i.e. 100 milliseconds and again sys.getswitchinterval() method is used to confirm the change −

import sys

# Set a longer thread switch interval
sys.setswitchinterval(0.1)
print(f"Thread switch interval set to: {sys.getswitchinterval()} seconds")

Output

Thread switch interval set to: 0.09999999999999999 seconds

Example 3

To compare the performance of a multi-threaded program with different thread switch intervals, We can run a simple benchmark where we set different intervals and measure the time taken for the threads to complete their tasks −

import sys
import threading
import time

def thread_task():
    count = 0
    for _ in range(1000000):
        count += 1

# Set short switch interval
sys.setswitchinterval(0.001)
start_time = time.time()
threads = [threading.Thread(target=thread_task) for _ in range(5)]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()
end_time = time.time()
print(f"Time taken with short switch interval: {end_time - start_time} seconds")

# Set long switch interval
sys.setswitchinterval(0.1)
start_time = time.time()
threads = [threading.Thread(target=thread_task) for _ in range(5)]
for thread in threads:
    thread.start()
for thread in threads:
    thread.join()
end_time = time.time()
print(f"Time taken with long switch interval: {end_time - start_time} seconds")

Output

Time taken with short switch interval: 0.2810394763946533 seconds
Time taken with long switch interval: 0.24994826316833496 seconds