Python-Code with threading runs sequentially instead of parallel if the main function contains a var-CodePudding

I found this simple example demonstrating how to use threading to parallelize opening multiple chrome sessions with selenium.

from selenium import webdriver
import threading
import time


def test_logic():
    driver = webdriver.Chrome()
    url = 'https://www.google.de'
    driver.get(url)
    # Implement your test logic
    time.sleep(2)
    driver.quit()

N = 5   # Number of browsers to spawn
thread_list = list()

# Start test
for i in range(N):
    t = threading.Thread(name='Test {}'.format(i), target=test_logic)
    t.start()
    time.sleep(1)
    print(t.name   ' started!')
    thread_list.append(t)

# Wait for all threads to complete
for thread in thread_list:
    thread.join()

print('Test completed!')

I tested it and it works. However if I modify the test_logic function to include a variable, i.e. j:

def test_logic(j):
    driver = webdriver.Chrome()
    url = 'https://www.google.de'
    driver.get(url)
    # Implement your test logic
    time.sleep(j)
    driver.quit()

and the corresponding part of threading to:

t = threading.Thread(name='Test {}'.format(i), target=test_logic(i))

the code will stop working in parallel and just runs sequentially.

I don't know what I might have not considered and therefore will be very grateful if anybody can give me some advices. Many thanks!

CodePudding user response：

target=test_logic(i) is invoking the function test_logic and give the return value to the thread.

You may want to do:

t = threading.Thread(name='Test {}'.format(i), target=test_logic, args=[i])

where target is the name of the function, and args is the arguments list for the function.

If you function has 2 args, like def test_logic(a,b), the args should contain 2 values.

More info in Python Thread Documentation

CodePudding user response：

You have to pass arguments to function as below:

t = threading.Thread(name='Test {}'.format(i), target=test_logic, args=(i,))